Systems and methods for multi-ap transmission with uniform coverage

ABSTRACT

A method for multiple access point (AP) transmission is disclosed. The method comprises receiving a repetition beacon from each of a plurality of APs, each received repetition beacon comprising a common information part and an AP-specific information part; decoding at least a subset of the received common information parts to obtain a first parameter; decoding the received AP-specific information parts to obtain a second parameter for each of the plurality of APs; performing a calculation based on the first parameter, the obtained second parameters and a number of the plurality of APs to obtain a calculation result; and transmitting a feedback based on the calculation result to the plurality of AP.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/815,753, filed Mar. 8, 2019, the contents of which are incorporatedherein by reference.

SUMMARY

A method for multiple access point (AP) transmission is disclosed. Themethod comprises: receiving a repetition beacon from each of a pluralityof APs, each received repetition beacon comprising a common informationpart and an AP-specific information part; decoding at least a subset ofthe received common information parts to obtain a first parameter;decoding the received AP-specific information parts to obtain a secondparameter for each of the plurality of APs; performing a calculationbased on the first parameter, the obtained second parameters and anumber of the plurality of APs to obtain a calculation result; andtransmitting a feedback based on the calculation result to the pluralityof APs.

A wireless transmit/receive unit (WTRU) for multiple access point (AP)transmission is disclosed. The WTRU comprises: a transceiver, configuredto receive a repetition beacon from each of a plurality of APs, eachreceived repetition beacon comprising a common information part and anAP-specific information part; and a processor, configured to decode atleast a subset of the received common information parts to obtain afirst parameter; decode the received AP-specific information parts toobtain a second parameter for each of the plurality of APs; and performa calculation based on the first parameter, the obtained secondparameters and a number of the plurality of APs to obtain a calculationresult, wherein the transceiver is further configured to transmit afeedback based on the calculation result to the plurality of APs.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawings,wherein like reference numerals in the figures indicate like elements,and wherein:

FIG. 1A is a system diagram illustrating an example communicationssystem in which one or more disclosed embodiments may be implemented;

FIG. 1B is a system diagram illustrating an example wirelesstransmit/receive unit (WTRU) that may be used within the communicationssystem illustrated in FIG. 1A according to an embodiment;

FIG. 1C is a system diagram illustrating an example radio access network(RAN) and an example core network (CN) that may be used within thecommunications system illustrated in FIG. 1A according to an embodiment;

FIG. 1D is a system diagram illustrating a further example RAN and afurther example CN that may be used within the communications systemillustrated in FIG. 1A according to an embodiment;

FIG. 2 illustrates an example of coordinated OFDMA fractional frequencyreuse (FFR);

FIG. 3 illustrates an example resource allocation associated withcoordinated OFDMA FFR;

FIG. 4 illustrates an example Coordinated Nulling/CoordinatedBeamforming (CN/CB) scenario;

FIG. 5 illustrates an example SU Joint Precoded Multi-AP transmission orCoordinated SU Beamforming scenario;

FIG. 6 illustrates an example MU Joint Precoded Multi-AP transmission orCoordinated MU Beamforming scenario;

FIG. 7 illustrates an example scenario for beacon transmission coverageof cell edge STAs;

FIG. 8 illustrates an architecture where STAs can associate with an APin the traditional way, or via a virtual AP;

FIG. 9 illustrates an architecture where STAs associate with the virtualAP only;

FIG. 10 illustrates multi-AP repetition beacons transmitted sequentiallyin different time slots;

FIG. 11 illustrates multi-AP repetition beacons transmittedconcurrently;

FIG. 12 illustrates an example where the leading AP may start themulti-AP repetition beacon transmission;

FIG. 13 illustrates an example where the leading AP may transmit amulti-AP beacon trigger frame;

FIG. 14 illustrates an example sequential transmission scheme withmultiple channels;

FIG. 15 illustrates an example of flexible repetition beacontransmissions with repetition beacon transmission interval;

FIG. 16 illustrates an example TBTT/beacon window and t_i;

FIG. 17 illustrates an example reservation/pad signal;

FIG. 18 illustrates example repetition beacon measurement and feedback;

FIG. 19 illustrates an example flow chart of a method according to anembodiment of this application;

FIG. 20 illustrates an example aggregated beacon structure;

FIG. 21 illustrates an example separated beacon structure;

FIG. 22 illustrates an example allowable transmission window to preventAP specific beacon overlap;

FIG. 23 illustrates an example non-allowed transmission window toprevent AP specific beacon overlap; and

FIG. 24 illustrates example single/multi-AP feedback polling/triggering.

DETAILED DESCRIPTION

FIG. 1A is a diagram illustrating an example communications system 100in which one or more disclosed embodiments may be implemented. Thecommunications system 100 may be a multiple access system that providescontent, such as voice, data, video, messaging, broadcast, etc., tomultiple wireless users. The communications system 100 may enablemultiple wireless users to access such content through the sharing ofsystem resources, including wireless bandwidth. For example, thecommunications systems 100 may employ one or more channel accessmethods, such as code division multiple access (CDMA), time divisionmultiple access (TDMA), frequency division multiple access (FDMA),orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), zero-tailunique-word discrete Fourier transform Spread OFDM (ZT-UW-DFT-S-OFDM),unique word OFDM (UW-OFDM), resource block-filtered OFDM, filter bankmulticarrier (FBMC), and the like.

As shown in FIG. 1A, the communications system 100 may include wirelesstransmit/receive units (WTRUs) 102 a, 102 b, 102 c, 102 d, a radioaccess network (RAN) 104, a core network (CN) 106, a public switchedtelephone network (PSTN) 108, the Internet 110, and other networks 112,though it will be appreciated that the disclosed embodiments contemplateany number of WTRUs, base stations, networks, and/or network elements.Each of the WTRUs 102 a, 102 b, 102 c, 102 d may be any type of deviceconfigured to operate and/or communicate in a wireless environment. Byway of example, the WTRUs 102 a, 102 b, 102 c, 102 d, any of which maybe referred to as a station (STA), may be configured to transmit and/orreceive wireless signals and may include a user equipment (UE), a mobilestation, a fixed or mobile subscriber unit, a subscription-based unit, apager, a cellular telephone, a personal digital assistant (PDA), asmartphone, a laptop, a netbook, a personal computer, a wireless sensor,a hotspot or Mi-Fi device, an Internet of Things (IoT) device, a watchor other wearable, a head-mounted display (HMD), a vehicle, a drone, amedical device and applications (e.g., remote surgery), an industrialdevice and applications (e.g., a robot and/or other wireless devicesoperating in an industrial and/or an automated processing chaincontexts), a consumer electronics device, a device operating oncommercial and/or industrial wireless networks, and the like. Any of theWTRUs 102 a, 102 b, 102 c and 102 d may be interchangeably referred toas a UE.

The communications systems 100 may also include a base station 114 aand/or a base station 114 b. Each of the base stations 114 a, 114 b maybe any type of device configured to wirelessly interface with at leastone of the WTRUs 102 a, 102 b, 102 c, 102 d to facilitate access to oneor more communication networks, such as the CN 106, the Internet 110,and/or the other networks 112. By way of example, the base stations 114a, 114 b may be a base transceiver station (BTS), a NodeB, an eNode B(eNB), a Home Node B, a Home eNode B, a next generation NodeB, such as agNode B (gNB), a new radio (NR) NodeB, a site controller, an accesspoint (AP), a wireless router, and the like. While the base stations 114a, 114 b are each depicted as a single element, it will be appreciatedthat the base stations 114 a, 114 b may include any number ofinterconnected base stations and/or network elements.

The base station 114 a may be part of the RAN 104, which may alsoinclude other base stations and/or network elements (not shown), such asa base station controller (BSC), a radio network controller (RNC), relaynodes, and the like. The base station 114 a and/or the base station 114b may be configured to transmit and/or receive wireless signals on oneor more carrier frequencies, which may be referred to as a cell (notshown). These frequencies may be in licensed spectrum, unlicensedspectrum, or a combination of licensed and unlicensed spectrum. A cellmay provide coverage for a wireless service to a specific geographicalarea that may be relatively fixed or that may change over time. The cellmay further be divided into cell sectors. For example, the cellassociated with the base station 114 a may be divided into threesectors. Thus, in one embodiment, the base station 114 a may includethree transceivers, i.e., one for each sector of the cell. In anembodiment, the base station 114 a may employ multiple-input multipleoutput (MIMO) technology and may utilize multiple transceivers for eachsector of the cell. For example, beamforming may be used to transmitand/or receive signals in desired spatial directions.

The base stations 114 a, 114 b may communicate with one or more of theWTRUs 102 a, 102 b, 102 c, 102 d over an air interface 116, which may beany suitable wireless communication link (e.g., radio frequency (RF),microwave, centimeter wave, micrometer wave, infrared (IR), ultraviolet(UV), visible light, etc.). The air interface 116 may be establishedusing any suitable radio access technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 104 and the WTRUs 102 a, 102b, 102 c may implement a radio technology such as Universal MobileTelecommunications System (UMTS) Terrestrial Radio Access (UTRA), whichmay establish the air interface 116 using wideband CDMA (WCDMA). WCDMAmay include communication protocols such as High-Speed Packet Access(HSPA) and/or Evolved HSPA (HSPA+). HSPA may include High-Speed Downlink(DL) Packet Access (HSDPA) and/or High-Speed Uplink (UL) Packet Access(HSUPA).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as Evolved UMTS TerrestrialRadio Access (E-UTRA), which may establish the air interface 116 usingLong Term Evolution (LTE) and/or LTE-Advanced (LTE-A) and/orLTE-Advanced Pro (LTE-A Pro).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement a radio technology such as NR Radio Access, which mayestablish the air interface 116 using NR.

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c may implement multiple radio access technologies. For example, thebase station 114 a and the WTRUs 102 a, 102 b, 102 c may implement LTEradio access and NR radio access together, for instance using dualconnectivity (DC) principles. Thus, the air interface utilized by WTRUs102 a, 102 b, 102 c may be characterized by multiple types of radioaccess technologies and/or transmissions sent to/from multiple types ofbase stations (e.g., an eNB and a gNB).

In other embodiments, the base station 114 a and the WTRUs 102 a, 102 b,102 c may implement radio technologies such as IEEE 802.11 (i.e.,Wireless Fidelity (WiFi), IEEE 802.16 (i.e., Worldwide Interoperabilityfor Microwave Access (WiMAX)), CDMA2000, CDMA2000 1X, CDMA2000 EV-DO,Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), InterimStandard 856 (IS-856), Global System for Mobile communications (GSM),Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and thelike.

The base station 114 b in FIG. 1A may be a wireless router, Home Node B,Home eNode B, or access point, for example, and may utilize any suitableRAT for facilitating wireless connectivity in a localized area, such asa place of business, a home, a vehicle, a campus, an industrialfacility, an air corridor (e.g., for use by drones), a roadway, and thelike. In one embodiment, the base station 114 b and the WTRUs 102 c, 102d may implement a radio technology such as IEEE 802.11 to establish awireless local area network (WLAN). In an embodiment, the base station114 b and the WTRUs 102 c, 102 d may implement a radio technology suchas IEEE 802.15 to establish a wireless personal area network (WPAN). Inyet another embodiment, the base station 114 b and the WTRUs 102 c, 102d may utilize a cellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE,LTE-A, LTE-A Pro, NR etc.) to establish a picocell or femtocell. Asshown in FIG. 1A, the base station 114 b may have a direct connection tothe Internet 110. Thus, the base station 114 b may not be required toaccess the Internet 110 via the CN 106.

The RAN 104 may be in communication with the CN 106, which may be anytype of network configured to provide voice, data, applications, and/orvoice over internet protocol (VoIP) services to one or more of the WTRUs102 a, 102 b, 102 c, 102 d. The data may have varying quality of service(QoS) requirements, such as differing throughput requirements, latencyrequirements, error tolerance requirements, reliability requirements,data throughput requirements, mobility requirements, and the like. TheCN 106 may provide call control, billing services, mobile location-basedservices, pre-paid calling, Internet connectivity, video distribution,etc., and/or perform high-level security functions, such as userauthentication. Although not shown in FIG. 1A, it will be appreciatedthat the RAN 104 and/or the CN 106 may be in direct or indirectcommunication with other RANs that employ the same RAT as the RAN 104 ora different RAT. For example, in addition to being connected to the RAN104, which may be utilizing a NR radio technology, the CN 106 may alsobe in communication with another RAN (not shown) employing a GSM, UMTS,CDMA 2000, WiMAX, E-UTRA, or WiFi radio technology.

The CN 106 may also serve as a gateway for the WTRUs 102 a, 102 b, 102c, 102 d to access the PSTN 108, the Internet 110, and/or the othernetworks 112. The PSTN 108 may include circuit-switched telephonenetworks that provide plain old telephone service (POTS). The Internet110 may include a global system of interconnected computer networks anddevices that use common communication protocols, such as thetransmission control protocol (TCP), user datagram protocol (UDP) and/orthe internet protocol (IP) in the TCP/IP internet protocol suite. Thenetworks 112 may include wired and/or wireless communications networksowned and/or operated by other service providers. For example, thenetworks 112 may include another CN connected to one or more RANs, whichmay employ the same RAT as the RAN 104 or a different RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities (e.g., theWTRUs 102 a, 102 b, 102 c, 102 d may include multiple transceivers forcommunicating with different wireless networks over different wirelesslinks). For example, the WTRU 102 c shown in FIG. 1A may be configuredto communicate with the base station 114 a, which may employ acellular-based radio technology, and with the base station 114 b, whichmay employ an IEEE 802 radio technology.

FIG. 1B is a system diagram illustrating an example WTRU 102. As shownin FIG. 1B, the WTRU 102 may include a processor 118, a transceiver 120,a transmit/receive element 122, a speaker/microphone 124, a keypad 126,a display/touchpad 128, non-removable memory 130, removable memory 132,a power source 134, a global positioning system (GPS) chipset 136,and/or other peripherals 138, among others. It will be appreciated thatthe WTRU 102 may include any sub-combination of the foregoing elementswhile remaining consistent with an embodiment.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), anyother type of integrated circuit (IC), a state machine, and the like.The processor 118 may perform signal coding, data processing, powercontrol, input/output processing, and/or any other functionality thatenables the WTRU 102 to operate in a wireless environment. The processor118 may be coupled to the transceiver 120, which may be coupled to thetransmit/receive element 122. While FIG. 1B depicts the processor 118and the transceiver 120 as separate components, it will be appreciatedthat the processor 118 and the transceiver 120 may be integratedtogether in an electronic package or chip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 116. For example, in one embodiment, thetransmit/receive element 122 may be an antenna configured to transmitand/or receive RF signals. In an embodiment, the transmit/receiveelement 122 may be an emitter/detector configured to transmit and/orreceive IR, UV, or visible light signals, for example. In yet anotherembodiment, the transmit/receive element 122 may be configured totransmit and/or receive both RF and light signals. It will beappreciated that the transmit/receive element 122 may be configured totransmit and/or receive any combination of wireless signals.

Although the transmit/receive element 122 is depicted in FIG. 1B as asingle element, the WTRU 102 may include any number of transmit/receiveelements 122. More specifically, the WTRU 102 may employ MIMOtechnology. Thus, in one embodiment, the WTRU 102 may include two ormore transmit/receive elements 122 (e.g., multiple antennas) fortransmitting and receiving wireless signals over the air interface 116.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as NR and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad 128 (e.g., a liquid crystal display (LCD) displayunit or organic light-emitting diode (OLED) display unit). The processor118 may also output user data to the speaker/microphone 124, the keypad126, and/or the display/touchpad 128. In addition, the processor 118 mayaccess information from, and store data in, any type of suitable memory,such as the non-removable memory 130 and/or the removable memory 132.The non-removable memory 130 may include random-access memory (RAM),read-only memory (ROM), a hard disk, or any other type of memory storagedevice. The removable memory 132 may include a subscriber identitymodule (SIM) card, a memory stick, a secure digital (SD) memory card,and the like. In other embodiments, the processor 118 may accessinformation from, and store data in, memory that is not physicallylocated on the WTRU 102, such as on a server or a home computer (notshown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries (e.g., nickel-cadmium (NiCd),nickel-zinc (NiZn), nickel metal hydride (NiMH), lithium-ion (Li-ion),etc.), solar cells, fuel cells, and the like.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 116 from abase station (e.g., base stations 114 a, 114 b) and/or determine itslocation based on the timing of the signals being received from two ormore nearby base stations. It will be appreciated that the WTRU 102 mayacquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include anaccelerometer, an e-compass, a satellite transceiver, a digital camera(for photographs and/or video), a universal serial bus (USB) port, avibration device, a television transceiver, a hands free headset, aBluetooth® module, a frequency modulated (FM) radio unit, a digitalmusic player, a media player, a video game player module, an Internetbrowser, a Virtual Reality and/or Augmented Reality (VR/AR) device, anactivity tracker, and the like. The peripherals 138 may include one ormore sensors. The sensors may be one or more of a gyroscope, anaccelerometer, a hall effect sensor, a magnetometer, an orientationsensor, a proximity sensor, a temperature sensor, a time sensor; ageolocation sensor, an altimeter, a light sensor, a touch sensor, amagnetometer, a barometer, a gesture sensor, a biometric sensor, ahumidity sensor and the like.

The WTRU 102 may include a full duplex radio for which transmission andreception of some or all of the signals (e.g., associated withparticular subframes for both the UL (e.g., for transmission) and DL(e.g., for reception) may be concurrent and/or simultaneous. The fullduplex radio may include an interference management unit to reduce andor substantially eliminate self-interference via either hardware (e.g.,a choke) or signal processing via a processor (e.g., a separateprocessor (not shown) or via processor 118). In an embodiment, the WTRU102 may include a half-duplex radio for which transmission and receptionof some or all of the signals (e.g., associated with particularsubframes for either the UL (e.g., for transmission) or the DL (e.g.,for reception)).

FIG. 1C is a system diagram illustrating the RAN 104 and the CN 106according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, 102c over the air interface 116. The RAN 104 may also be in communicationwith the CN 106.

The RAN 104 may include eNode-Bs 160 a, 160 b, 160 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 160 a, 160 b, 160c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the eNode-Bs 160 a, 160 b, 160 c may implement MIMO technology. Thus,the eNode-B 160 a, for example, may use multiple antennas to transmitwireless signals to, and/or receive wireless signals from, the WTRU 102a.

Each of the eNode-Bs 160 a, 160 b, 160 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the UL and/or DL, and the like. As shown in FIG. 1C, the eNode-Bs 160a, 160 b, 160 c may communicate with one another over an X2 interface.

The CN 106 shown in FIG. 1C may include a mobility management entity(MME) 162, a serving gateway (SGW) 164, and a packet data network (PDN)gateway (PGW) 166. While the foregoing elements are depicted as part ofthe CN 106, it will be appreciated that any of these elements may beowned and/or operated by an entity other than the CN operator.

The MME 162 may be connected to each of the eNode-Bs 162 a, 162 b, 162 cin the RAN 104 via an S1 interface and may serve as a control node. Forexample, the MME 162 may be responsible for authenticating users of theWTRUs 102 a, 102 b, 102 c, bearer activation/deactivation, selecting aparticular serving gateway during an initial attach of the WTRUs 102 a,102 b, 102 c, and the like. The MME 162 may provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as GSM and/or WCDMA.

The SGW 164 may be connected to each of the eNode Bs 160 a, 160 b, 160 cin the RAN 104 via the S1 interface. The SGW 164 may generally route andforward user data packets to/from the WTRUs 102 a, 102 b, 102 c. The SGW164 may perform other functions, such as anchoring user planes duringinter-eNode B handovers, triggering paging when DL data is available forthe WTRUs 102 a, 102 b, 102 c, managing and storing contexts of theWTRUs 102 a, 102 b, 102 c, and the like.

The SGW 164 may be connected to the PGW 166, which may provide the WTRUs102 a, 102 b, 102 c with access to packet-switched networks, such as theInternet 110, to facilitate communications between the WTRUs 102 a, 102b, 102 c and IP-enabled devices.

The CN 106 may facilitate communications with other networks. Forexample, the CN 106 may provide the WTRUs 102 a, 102 b, 102 c withaccess to circuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. For example, the CN 106 may include,or may communicate with, an IP gateway (e.g., an IP multimedia subsystem(IMS) server) that serves as an interface between the CN 106 and thePSTN 108. In addition, the CN 106 may provide the WTRUs 102 a, 102 b,102 c with access to the other networks 112, which may include otherwired and/or wireless networks that are owned and/or operated by otherservice providers.

Although the WTRU is described in FIGS. 1A-1D as a wireless terminal, itis contemplated that in certain representative embodiments that such aterminal may use (e.g., temporarily or permanently) wired communicationinterfaces with the communication network.

In representative embodiments, the other network 112 may be a WLAN.

A WLAN in Infrastructure Basic Service Set (BSS) mode may have an AccessPoint (AP) for the BSS and one or more stations (STAs) associated withthe AP. The AP may have access or an interface to a Distribution System(DS) or another type of wired/wireless network that carries traffic into and/or out of the BSS. Traffic to STAs that originates from outsidethe BSS may arrive through the AP and may be delivered to the STAs.Traffic originating from STAs to destinations outside the BSS may besent to the AP to be delivered to respective destinations. Trafficbetween STAs within the BSS may be sent through the AP, for example,where the source STA may send traffic to the AP and the AP may deliverthe traffic to the destination STA. The traffic between STAs within aBSS may be considered and/or referred to as peer-to-peer traffic. Thepeer-to-peer traffic may be sent between (e.g., directly between) thesource and destination STAs with a direct link setup (DLS). In certainrepresentative embodiments, the DLS may use an 802.11e DLS or an 802.11ztunneled DLS (TDLS). A WLAN using an Independent BSS (IBSS) mode may nothave an AP, and the STAs (e.g., all of the STAs) within or using theIBSS may communicate directly with each other. The IBSS mode ofcommunication may sometimes be referred to herein as an “ad-hoc” mode ofcommunication.

When using the 802.11ac infrastructure mode of operation or a similarmode of operations, the AP may transmit a beacon on a fixed channel,such as a primary channel. The primary channel may be a fixed width(e.g., 20 MHz wide bandwidth) or a dynamically set width. The primarychannel may be the operating channel of the BSS and may be used by theSTAs to establish a connection with the AP. In certain representativeembodiments, Carrier Sense Multiple Access with Collision Avoidance(CSMA/CA) may be implemented, for example in 802.11 systems. ForCSMA/CA, the STAs (e.g., every STA), including the AP, may sense theprimary channel. If the primary channel is sensed/detected and/ordetermined to be busy by a particular STA, the particular STA may backoff. One STA (e.g., only one station) may transmit at any given time ina given BSS.

High Throughput (HT) STAs may use a 40 MHz wide channel forcommunication, for example, via a combination of the primary 20 MHzchannel with an adjacent or nonadjacent 20 MHz channel to form a 40 MHzwide channel.

Very High Throughput (VHT) STAs may support 20MHz, 40 MHz, 80 MHz,and/or 160 MHz wide channels. The 40 MHz, and/or 80 MHz, channels may beformed by combining contiguous 20 MHz channels. A 160 MHz channel may beformed by combining 8 contiguous 20 MHz channels, or by combining twonon-contiguous 80 MHz channels, which may be referred to as an 80+80configuration. For the 80+80 configuration, the data, after channelencoding, may be passed through a segment parser that may divide thedata into two streams. Inverse Fast Fourier Transform (IFFT) processing,and time domain processing, may be done on each stream separately. Thestreams may be mapped on to the two 80 MHz channels, and the data may betransmitted by a transmitting STA. At the receiver of the receiving STA,the above described operation for the 80+80 configuration may bereversed, and the combined data may be sent to the Medium Access Control(MAC).

Sub 1 GHz modes of operation are supported by 802.11af and 802.11ah. Thechannel operating bandwidths, and carriers, are reduced in 802.11af and802.11ah relative to those used in 802.11n, and 802.11ac. 802.11afsupports 5 MHz, 10 MHz, and 20 MHz bandwidths in the TV White Space(TVWS) spectrum, and 802.11ah supports 1 MHz, 2 MHz, 4 MHz, 8 MHz, and16 MHz bandwidths using non-TVWS spectrum. According to a representativeembodiment, 802.11ah may support Meter Type Control/Machine-TypeCommunications (MTC), such as MTC devices in a macro coverage area. MTCdevices may have certain capabilities, for example, limited capabilitiesincluding support for (e.g., only support for) certain and/or limitedbandwidths. The MTC devices may include a battery with a battery lifeabove a threshold (e.g., to maintain a very long battery life).

WLAN systems, which may support multiple channels, and channelbandwidths, such as 802.11n, 802.11ac, 802.11af, and 802.11ah, include achannel which may be designated as the primary channel. The primarychannel may have a bandwidth equal to the largest common operatingbandwidth supported by all STAs in the BSS. The bandwidth of the primarychannel may be set and/or limited by a STA, from among all STAs inoperating in a BSS, which supports the smallest bandwidth operatingmode. In the example of 802.11ah, the primary channel may be 1 MHz widefor STAs (e.g., MTC type devices) that support (e.g., only support) a 1MHz mode, even if the AP, and other STAs in the BSS support 2 MHz, 4MHz, 8 MHz, 16 MHz, and/or other channel bandwidth operating modes.Carrier sensing and/or Network Allocation Vector (NAV) settings maydepend on the status of the primary channel. If the primary channel isbusy, for example, due to a STA (which supports only a 1 MHz operatingmode) transmitting to the AP, all available frequency bands may beconsidered busy even though a majority of the available frequency bandsremains idle.

In the United States, the available frequency bands, which may be usedby 802.11ah, are from 902 MHz to 928 MHz. In Korea, the availablefrequency bands are from 917.5 MHz to 923.5 MHz. In Japan, the availablefrequency bands are from 916.5 MHz to 927.5 MHz. The total bandwidthavailable for 802.11ah is 6 MHz to 26 MHz depending on the country code.

FIG. 1D is a system diagram illustrating the RAN 104 and the CN 106according to an embodiment. As noted above, the RAN 104 may employ an NRradio technology to communicate with the WTRUs 102 a, 102 b, 102 c overthe air interface 116. The RAN 104 may also be in communication with theCN 106.

The RAN 104 may include gNBs 180 a, 180 b, 180 c, though it will beappreciated that the RAN 104 may include any number of gNBs whileremaining consistent with an embodiment. The gNBs 180 a, 180 b, 180 cmay each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In one embodiment,the gNBs 180 a, 180 b, 180 c may implement MIMO technology. For example,gNBs 180 a, 108 b may utilize beamforming to transmit signals to and/orreceive signals from the gNBs 180 a, 180 b, 180 c. Thus, the gNB 180 a,for example, may use multiple antennas to transmit wireless signals to,and/or receive wireless signals from, the WTRU 102 a. In an embodiment,the gNBs 180 a, 180 b, 180 c may implement carrier aggregationtechnology. For example, the gNB 180 a may transmit multiple componentcarriers to the WTRU 102 a (not shown). A subset of these componentcarriers may be on unlicensed spectrum while the remaining componentcarriers may be on licensed spectrum. In an embodiment, the gNBs 180 a,180 b, 180 c may implement Coordinated Multi-Point (CoMP) technology.For example, WTRU 102 a may receive coordinated transmissions from gNB180 a and gNB 180 b (and/or gNB 180 c).

The WTRUs 102 a, 102 b, 102 c may communicate with gNBs 180 a, 180 b,180 c using transmissions associated with a scalable numerology. Forexample, the OFDM symbol spacing and/or OFDM subcarrier spacing may varyfor different transmissions, different cells, and/or different portionsof the wireless transmission spectrum. The WTRUs 102 a, 102 b, 102 c maycommunicate with gNBs 180 a, 180 b, 180 c using subframe or transmissiontime intervals (TTIs) of various or scalable lengths (e.g., containing avarying number of OFDM symbols and/or lasting varying lengths ofabsolute time).

The gNBs 180 a, 180 b, 180 c may be configured to communicate with theWTRUs 102 a, 102 b, 102 c in a standalone configuration and/or anon-standalone configuration. In the standalone configuration, WTRUs 102a, 102 b, 102 c may communicate with gNBs 180 a, 180 b, 180 c withoutalso accessing other RANs (e.g., such as eNode-Bs 160 a, 160 b, 160 c).In the standalone configuration, WTRUs 102 a, 102 b, 102 c may utilizeone or more of gNBs 180 a, 180 b, 180 c as a mobility anchor point. Inthe standalone configuration, WTRUs 102 a, 102 b, 102 c may communicatewith gNBs 180 a, 180 b, 180 c using signals in an unlicensed band. In anon-standalone configuration WTRUs 102 a, 102 b, 102 c may communicatewith/connect to gNBs 180 a, 180 b, 180 c while also communicatingwith/connecting to another RAN such as eNode-Bs 160 a, 160 b, 160 c. Forexample, WTRUs 102 a, 102 b, 102 c may implement DC principles tocommunicate with one or more gNBs 180 a, 180 b, 180 c and one or moreeNode-Bs 160 a, 160 b, 160 c substantially simultaneously. In thenon-standalone configuration, eNode-Bs 160 a, 160 b, 160 c may serve asa mobility anchor for WTRUs 102 a, 102 b, 102 c and gNBs 180 a, 180 b,180 c may provide additional coverage and/or throughput for servicingWTRUs 102 a, 102 b, 102 c.

Each of the gNBs 180 a, 180 b, 180 c may be associated with a particularcell (not shown) and may be configured to handle radio resourcemanagement decisions, handover decisions, scheduling of users in the ULand/or DL, support of network slicing, DC, interworking between NR andE-UTRA, routing of user plane data towards User Plane Function (UPF) 184a, 184 b, routing of control plane information towards Access andMobility Management Function (AMF) 182 a, 182 b and the like. As shownin FIG. 1D, the gNBs 180 a, 180 b, 180 c may communicate with oneanother over an Xn interface.

The CN 106 shown in FIG. 1D may include at least one AMF 182 a, 182 b,at least one UPF 184 a, 184 b, at least one Session Management Function(SMF) 183 a, 183 b, and possibly a Data Network (DN) 185 a, 185 b. Whilethe foregoing elements are depicted as part of the CN 106, it will beappreciated that any of these elements may be owned and/or operated byan entity other than the CN operator.

The AMF 182 a, 182 b may be connected to one or more of the gNBs 180 a,180 b, 180 c in the RAN 104 via an N2 interface and may serve as acontrol node. For example, the AMF 182 a, 182 b may be responsible forauthenticating users of the WTRUs 102 a, 102 b, 102 c, support fornetwork slicing (e.g., handling of different protocol data unit (PDU)sessions with different requirements), selecting a particular SMF 183 a,183 b, management of the registration area, termination of non-accessstratum (NAS) signaling, mobility management, and the like. Networkslicing may be used by the AMF 182 a, 182 b in order to customize CNsupport for WTRUs 102 a, 102 b, 102 c based on the types of servicesbeing utilized WTRUs 102 a, 102 b, 102 c. For example, different networkslices may be established for different use cases such as servicesrelying on ultra-reliable low latency (URLLC) access, services relyingon enhanced massive mobile broadband (eMBB) access, services for MTCaccess, and the like. The AMF 182 a, 182 b may provide a control planefunction for switching between the RAN 104 and other RANs (not shown)that employ other radio technologies, such as LTE, LTE-A, LTE-A Pro,and/or non-3GPP access technologies such as WiFi.

The SMF 183 a, 183 b may be connected to an AMF 182 a, 182 b in the CN106 via an N11 interface. The SMF 183 a, 183 b may also be connected toa UPF 184 a, 184 b in the CN 106 via an N4 interface. The SMF 183 a, 183b may select and control the UPF 184 a, 184 b and configure the routingof traffic through the UPF 184 a, 184 b. The SMF 183 a, 183 b mayperform other functions, such as managing and allocating UE IP address,managing PDU sessions, controlling policy enforcement and QoS, providingDL data notifications, and the like. A PDU session type may be IP-based,non-IP based, Ethernet-based, and the like.

The UPF 184 a, 184 b may be connected to one or more of the gNBs 180 a,180 b, 180 c in the RAN 104 via an N3 interface, which may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between the WTRUs 102a, 102 b, 102 c and IP-enabled devices. The UPF 184, 184 b may performother functions, such as routing and forwarding packets, enforcing userplane policies, supporting multi-homed PDU sessions, handling user planeQoS, buffering DL packets, providing mobility anchoring, and the like.

The CN 106 may facilitate communications with other networks. Forexample, the CN 106 may include, or may communicate with, an IP gateway(e.g., an IP multimedia subsystem (IMS) server) that serves as aninterface between the CN 106 and the PSTN 108. In addition, the CN 106may provide the WTRUs 102 a, 102 b, 102 c with access to the othernetworks 112, which may include other wired and/or wireless networksthat are owned and/or operated by other service providers. In oneembodiment, the WTRUs 102 a, 102 b, 102 c may be connected to a local DN185 a, 185 b through the UPF 184 a, 184 b via the N3 interface to theUPF 184 a, 184 b and an N6 interface between the UPF 184 a, 184 b andthe DN 185 a, 185 b.

In view of FIGS. 1A-1D, and the corresponding description of FIGS.1A-1D, one or more, or all, of the functions described herein withregard to one or more of: WTRU 102 a-d, Base Station 114 a-b, eNode-B160 a-c, MME 162, SGW 164, PGW 166, gNB 180 a-c, AMF 182 a-b, UPF 184a-b, SMF 183 a-b, DN 185 a-b, and/or any other device(s) describedherein, may be performed by one or more emulation devices (not shown).The emulation devices may be one or more devices configured to emulateone or more, or all, of the functions described herein. For example, theemulation devices may be used to test other devices and/or to simulatenetwork and/or WTRU functions.

The emulation devices may be designed to implement one or more tests ofother devices in a lab environment and/or in an operator networkenvironment. For example, the one or more emulation devices may performthe one or more, or all, functions while being fully or partiallyimplemented and/or deployed as part of a wired and/or wirelesscommunication network in order to test other devices within thecommunication network. The one or more emulation devices may perform theone or more, or all, functions while being temporarilyimplemented/deployed as part of a wired and/or wireless communicationnetwork. The emulation device may be directly coupled to another devicefor purposes of testing and/or performing testing using over-the-airwireless communications.

The one or more emulation devices may perform the one or more, includingall, functions while not being implemented/deployed as part of a wiredand/or wireless communication network. For example, the emulationdevices may be utilized in a testing scenario in a testing laboratoryand/or a non-deployed (e.g., testing) wired and/or wirelesscommunication network in order to implement testing of one or morecomponents. The one or more emulation devices may be test equipment.Direct RF coupling and/or wireless communications via RF circuitry(e.g., which may include one or more antennas) may be used by theemulation devices to transmit and/or receive data.

In a typical 802.11 network, STAs are associated with a single AP andtransmit to and from that AP with little or no coordination withtransmissions in neighboring BSSs. A STA may defer to an overlapping BSS(OBSS) transmission based on a CSMA protocol that is entirelyindependent between BSSs. 802.11ax systems may support some level ofcoordination between OBSSs by spatial re-use procedures to allow OBSStransmissions based on an adjusted energy detection threshold (using theOBSS packet detection (PD) procedure) or by knowledge of the amount ofinterference that could be tolerated by a receiving OBSS STA (using thespatial reuse parameter (SRP) procedure). In this application, unlessotherwise indicated, the terms STA and WTRU may be used interchangeably.

Some embodiments facilitate more coordination between OBSSs, e.g., byallowing transmission from multiple APs to a single or multiple STAs.Among other things, this may be distinguished from CoordinatedMulti-point (CoMP) transmissions in 3GPP LTE Release 10. For example,the coordination between OBSSs may be implemented using an unlicensedband and may be specific to the 802.11 protocol.

In CoMP, multiple eNBs may transmit to the same or multiple WTRUs in thesame time and frequency resource using joint processing/transmission,with the objective of improving the overall throughput for theconsidered WTRU. Dynamic cell selection may be treated as a special caseof joint processing in which only one of the set of eNBs is activelytransmitting data at any time. On the other hand, multiple eNBs maytransmit to different WTRUs (each eNB serving its own WTRU) in the sametime and frequency resource using coordinated beamforming/scheduling,with the objective of reducing interference experienced by each WTRU.Significant improvements of cell average and/or cell edge throughput maybe achieved due to CoMP in LTE. Multiple transmit antennas may beassumed to be available for each base station. Simultaneous interferencesuppression (for other WTRUs) and signal quality optimization (for thedesired WTRU) may be performed through spatial domain signal processingat each base station.

In general, some degree of channel state information may be assumed tobe available at the base stations, e.g., through explicit feedback.Further, a certain degree of timing and/or frequency synchronization maybe assumed such that more complicated signal processing to deal withinter-carrier interference (or inter-symbol interference) may beavoided. Further, the level of coordination between the eNBs may affectwhich specific CoMP scheme that may be possible.

Multi-AP transmission schemes in WLANs may be classified, e.g., asCoordinated OFDMA, Coordinated Nulling/Coordinated Beamforming (CN/CB),and/or Coordinated SU/MU Transmission. In the case of Coordinated SUTransmission, multiple APs transmit to a STA in one resource unit (RU).Coordinated SU transmission may include one or more of (in order ofincreased complexity) Dynamic Point Selection, Coordinated SUBeamforming, and/or Coordinated MU Beamforming. In the case of DynamicPoint Selection, the transmission may be dynamically selected from oneof the set of APs. Note that this may include HARQ. In the case ofCoordinated SU Beamforming, the transmission is from the multiple APssimultaneously and the transmission may be beamformed. In the case ofCoordinated MU Beamforming, multiple APs transmit or receive datato/from multiple STAs on one RU.

In coordinated OFDMA, each group of RUs may be used by one AP only totransmit or receive data. The information may be beamformed or haveMU-MIMO on each RU. Complexity may be characterized as relatively low tomedium. In a simple coordinated OFDMA scheme, APs may divide the OFDMARUs between themselves in a coordinated manner, for example, with eachAP restricted to specific RUs. A more sophisticated scheme may occur inwhich the APs allow STAs that are not affected by interference, or willnot affect others, to utilize the entire bandwidth while restrictingaccess for the STAs that may be affected. This may be referred to asfractional frequency reuse (FFR). FIG. 2 illustrates an example ofcoordinated OFDMA FFR. FIG. 3 illustrates an example resource allocationassociated with coordinated OFDMA FFR.

In Coordinated Nulling/Coordinated Beamforming (CN/CB), each AP mayapply precoding to transmit information to or receive from its desiredSTA or STAs and to suppress interference to or from other STA(s). FIG. 4illustrates an example CN/CB scenario. As shown in FIG. 4, AP1 maytransmit information to or receive from its desired STA, i.e., STA1, andAP2 may transmit information to or receive from its desired STA, i.e.,STA2. AP1 may suppress interference to or from STA2, and AP2 maysuppress interference to or from STA2. It is noted that in this case,the data for each STA may only be needed at its associated AP althoughin some implementations channel information from the other STA may beneeded at both APs.

In coordinated SU or MU (SU/MU) transmission, multiple APs maycoordinate to transmit information to or receive information from asingle STA or multiple STAs simultaneously. In this case, both thechannel information and the data for the STA(s) may be needed at bothAPs. Coordinated SU/MU transmission may include Coordinated SUTransmission and/or Coordinated MU Beamforming.

In Coordinated SU Transmission, multiple APs may transmit to a STA inone RU. Coordinated SU transmission may include, (in order of increasedcomplexity): Dynamic Point Selection, and/or Coordinated SU Beamformingor Joint Precoding. In Dynamic Point Selection, the transmission may bedynamically selected from one of the set of APs. This selection mayincorporate HARQ. In Coordinated SU Beamforming or Joint Precoding, thetransmission may be from the multiple APs simultaneously and thetransmission may be beamformed or precoded to the desired STA on one ormore RUs. FIG. 5 illustrates an example SU Joint Precoded Multi-APtransmission or Coordinated SU Beamforming scenario. As shown in FIG. 5,there are two APs (AP1 and AP2) and only one STA (STA1). AP1 and AP2 maydo transmission to STA1 simultaneously and the transmission may bebeamformed or precoded to the STA1 on one or more RUs.

In Coordinated MU Beamforming, multiple APs may transmit or receive datato/from multiple STAs on one or more RUs. FIG. 6 illustrates an exampleMU Joint Precoded Multi-AP transmission or Coordinated MU Beamformingscenario. As shown in FIG. 6, there are two APs (AP1 and AP2) and twoSTAs (STA1 and STA2). Each AP may transmit or receive data to/from thetwo STAs.

Some embodiments discussed herein are directed to Joint Multi-APTransmission scenarios. The following description will describe someproblems and technical solutions to solve the problems according to thisapplication. The following description will first describe technicalproblems to be solved by this application.

Problem 1: some embodiments discussed herein relate to overhead inmulti-AP transmission. With multi-AP communication networks, data to aSTA may be transmitted from multiple APs at the same time in thedownlink, and data from a STA may be transmitted to multiple APs at thesame time in the uplink. To enable such capability, a STA may need toassociate with multiple APs to enable multi-AP transmission/reception atthe same time. The traditional AP-STA association protocol does notfacilitate this, as each STA can only associate with one AP at a giventime. Accordingly, it may be desirable to develop a more efficientmethod to achieve multi-AP association.

Problem 2: in some embodiments, multiple APs may coordinate to achievehigher peak throughput and increased efficiency as well as better BSSedge coverage (e.g., multi-AP schemes may be used to reach STAs in celledge). Preferably, some embodiments may address fairness to and coverageof a cell edge STA. In a single AP scenario, a STA may normally onlylisten to a beacon from one AP, and STAs at the edge of the coveragearea an AP may have difficulty in decoding normal Beacon transmissions.Accordingly, for multi-AP capability in a network, it may be desired toprovide schemes and mechanisms to extend the coverage range for beacontransmission and reception. FIG. 7 illustrates an exemplary scenario forbeacon transmission coverage of cell edge STAs. In FIG. 7, the arrowindicates a STA at the edge. In some implementations, the STA may bereached by joint transmission. In some implementations, the STA may ormay not be able to receive normal beacons.

Problem 3: some embodiments discussed herein relate to timesynchronisation (e.g., a TSF) when receiving from multiple APs. Inmulti-AP transmission, if a cell edge STA receives a joint transmissionfrom all APs in the virtual AP set for a beacon frame at the same time,the time synchronization function at the STA may behave in the same wayas a legacy STA. However, each AP has its own busy/idle medium status attarget beacon transmission time (TBTT), and not all of the APs may beable to perform a joint transmission at the desired time. In this case,the transmission time of beacon frames from different APs may bestaggered. Even if it is possible to transmit a joint transmission fromall APs in a virtual AP set/multi-AP set, a cell edge STA may still notbe able to receive it, e.g., due to local interference from an OBSS. Inthis case, it may be beneficial for APs to intentionally stagger theirbeacon transmissions in time for increased diversity, e.g., in terms ofinterference.

When beacons are transmitted at different time, Timestamp fields in themare supposed to be different. Given the rest of the contents are thesame among the beacons in the same BI, different Timestamp fieldscreates different PSDUs. This prevents PHY method from effectivelycombining the signals.

In some embodiments, to overcome this, all APs may use the Timestamp ofa particular beacon frame (e.g., the first beacon transmitted in the BI)in their transmitted beacon frame or frames. This may require both APsand STAs to be able to at least detect the transmission of this beaconframe however, and may require APs to be able to decode this particularframe. This approach may result in multiple beacons transmitted atdifferent times. However, if a STA cannot detect the first beacon (e.g.,due to a collision), then the timing synchronization function (TSF) isnot updated in this beacon interval (BI) or it may be updated based onsecond or later beacons. This may hinder the objects of time diversityfrom transmitting multiple beacons in time, e.g., due to this weaknessin the particular transmission at the moment of the timestamp.

Problem 4: some embodiments discussed herein relate to multi-AP spatialpuncturing. Multi-AP transmission and reception may involve a group ofAPs transmitting to and receiving from STAs. In some cases, it may notbe necessary for all APs in the group to join a particular transmissionto or reception from a STA. In some implementations, the STA mayfacilitate the group of APs in a dynamic AP selection scheme such thatonly a subset of the APs is utilized.

The following description will first describe methods and procedures tosolve the above-mentioned problem 1. That is, methods and proceduresherein disclosed address the issues discussed above relating to overheadin multi-AP transmission. To enable multi-AP transmissions, multiple APsor a group of APs may form a “virtual AP” with a shared virtual basicservice set identifier (vBSSID) and/or virtual service set identifier(vSSID). A STA may associate with the group of APs using the vBSSIDand/or vSSID without knowing that it is a group of APs. FIG. 8 and FIG.9 illustrate exemplary virtual AP architectures. FIG. 8 illustrates anarchitecture where STAs can associate with an AP in the traditional way,or associate with a group of APs via a virtual AP. FIG. 9 illustrates anarchitecture where STAs associate with a group of APs via a virtual APonly.

In the example of FIG. 8, each AP may have its own BSS. In addition, thegroup of APs may have a virtual AP. STAs may associate with thetraditional single AP or with the virtual AP. As shown in FIG. 8, thoseSTAs located at the edge of a BSS coverage area may associate with thevirtual AP, and those STAs not located at a BSS coverage area mayassociate with an AP in the traditional way.

In the example of FIG. 9, each AP may not have its own BSS. The group ofAPs may have a virtual AP. STAs may associate with the virtual AP. Incases where multi-AP spatial puncturing is allowed, a STA may not alwayscommunicate with all the APs in the virtual AP group; rather, it maycommunicate with a subset of APs, and the rest of APs in the group maybe considered as punctured.

A STA which associates with the virtual AP may have an associationidentifier (AID) assigned by the virtual AP. The group of APs may usethis AID to refer the STA. In cases where a larger number of STAsassociate with a virtual AP, the number of bits representing an AID maybe increased. In some embodiments, a basic AID and an AID extension maybe used to uniquely represent a STA in the BSS. The basic AID may be thesame size as current AIDs discussed above, and the AID extension may beused if the number of STAs in the BSS is bigger than a threshold.

In DL virtual AP transmissions from a virtual AP to a STA, the trafficto the STA may be passed to all the related APs. The related APs mayinclude all the APs in the virtual AP group, or a subset of APs used tocommunicate with the STA. In this way, the traffic may be readied fortransmission from multiple APs to the STA. It should be noted that theabove-mentioned embodiments regarding the DL virtual AP transmission isonly given by way of example, and they are not intended to be exclusiveor be limiting to the present application. The DL virtual APtransmission may be implemented in any other available ways as long asthey may follow the principle and guideline discussed above.

In UL virtual AP transmission from a STA to a virtual AP, a packet(e.g., the received physical layer convergence protocol (PLOP) protocoldata unit (PPDU)) transmitted from the STA may be received by all or asubset of the related APs. Each AP may process the packet partially andmay pass the packet to a backhaul, where more PHY layer processes may beperformed at the backhaul. In some embodiments, each AP may identifythat the reception may involve multiple APs, and accordingly the AP maypass the packet to backhaul. The backhaul may perform combination of allreceived valid packets and decoding. In some embodiments, each AP mayidentify that reception may involve multiple APs, and accordingly the APmay perform channel estimation and demodulation, and pass thedemodulated soft bits, (e.g., log likelihood ratio (LLR)), to abackhaul. The backhaul may perform LLR combination and channel decoding.In some embodiments, each AP may identify that the reception may involvemultiple APs, and the AP may attempt to detect and decode the packet(e.g., PPDU). If the AP succeeds in detecting and decoding the packet,it may pass the decoded MAC packet to the backhaul; otherwise, it maypass the received packet or demodulated soft bits to the backhaul. Itshould be noted that the above-mentioned embodiments regarding the ULvirtual AP transmission is only given by way of example, and they arenot intended to be exclusive or be limiting to the present application.The UL virtual AP transmission may be implemented in any other availableways as long as they may follow the principle and guideline discussedabove.

The figures and description above may assume a backhaul connectionbetween the APs. However, the APs may be connected and controlled by acentral controller or in any suitable manner. In the central controllercase, the backhaul may be replaced by the central controller. Theconnection may be wired or wireless. In the case of a wirelessconnection, the connection may share the same band/channel as the BSSband/channel or may use a different band/channel.

The following technical solution is directed to solve theabove-mentioned problems 1 and 2. That is, some embodiments disclosedbelow include multi-AP active scanning in order to solve theabove-mentioned problems 1 and 2. An exemplary multi-AP active scanningprocedure may proceed according to one or more of the following schemes.

An AP (which may be part of a Multi-AP set SSID, where the AP may be themaster AP or a slave AP) may include one or more of the followinginformation in its beacon, short beacon, FILS Discovery frame, and/or(broadcast) probe responses: Virtual BSSID, SSID, Multi-AP beaconschedule, Preferred Scanning methods, and/or Members of the sameMulti-AP set. The above-mentioned information will be further describedas follows.

A virtual BSSID may represent the entire multi-STA set SS. The VirtualBSSID may be used by the STA to send a Probe Request or Authenticationor Association Request in order to obtain information or conductauthentication and/or association with the Multi-STA set SS.

An SSID may represent the entire multi-STA set SS. The SSID may be usedby the STA to send a Probe Request or Authentication or AssociationRequest in order to get information or conduct authentication and/orassociation with the Multi-STA set SS.

A Multi-AP beacon schedule may indicate the schedule by which beacons ormulti-AP beacons, FILS discovery frames, Probe responses, may betransmitted concurrently or sequentially by one or more APs within themulti-AP set SS. The multi-AP beacon schedule may be indicated in termsof an offset to the TSF timer, which may also be included in the proberesponse, or an offset to the end of the current frame. The multi-APbeacon schedule may also or alternatively include the schedule oftriggered multi-AP beacon frames, and/or multi-AP probe response frames,or FILS discovery frames.

Preferred Scanning methods may indicate the preferred method forscanning, including multi-AP active scanning, passive scanning, singleAP active scanning, etc. Members of the same Multi-AP set may indicateone or more APs within the same Multi-AP set. Alternatively oradditionally, the AP may include this information within the reducedneighbor report, or co-located or co-hosted APs, e.g., with anindication that it is within the same multi-AP set SS.

It should be noted that those above-mentioned information which may beincluded in an AP's beacon, short beacon, FILS Discovery frame, and/or(broadcast) probe responses is only given by way of example, and it isnot intended to be exclusive or be limiting to the present application.Any other available information may be included as long as it may followthe above-discussed principle and guideline.

The above-mentioned information may be included in one or more of thefollowing fields or elements: Multi-AP element, Reduced Neighbor Report,Neighbor report, Multi-band report, 6 GHz discovery element, and/or Outof band assistance Discovery element. The information may be transmittedin the bands or frequency channels other than the bands or frequency onwhich the beacon is transmitted. Other neighboring APs or BSSs mayinclude such information overheard from other APs information, e.g., intheir own Multi-AP element, Reduced Neighbor report, Neighbor report, orother fields.

A STA may initiate a multi-AP active scanning procedure by sending aprobe request frame, which may include a Multi-AP Capability element.The Multi-AP Capability element may include a list of Multi-APcapabilities of which the STA is capable, e.g., multi-AP jointtransmission, multi-AP MIMO, multi-AP MU-MIMO, multi-AP HARQ, multi-APdynamic AP selection, multi-AP spatial puncturing, multi-AP spatialnulling, etc., in uplink and/or in downlink. The Multi-AP capabilitieselement may also indicate how many APs the STA is capable of supportingconcurrently.

The Probe Request frame may include a SSID, BSSID or a virtual BSSID.The SSID, BSSID or virtual BSSID may be used to identify a multi-AP set.The scanning STA may have acquired the information regarding SSID, BSSIDor virtual BSSID through a prior association, or through pre-acquiredknowledge such as through FILS discovery frames, or from Neighbor Reportor Reduced Neighbor Report, or through a 6 GHz discovery element, or anassistant discovery element that may be transmitted by another AP and/orco-hosted or co-located AP, or on a different channel or different band.The Probe Request frame may include an indication indicating that it isrequesting a multi-AP probe response, or a multi-AP response, which maybe included in the Multi-AP Capabilities element or Multi-AP Requestelement.

In cases where an AP is part of a Multi-AP set SSID, where the AP may bethe master AP or a slave AP, it may respond to the Probe Request in thefollowing way.

If the Probe Request includes a multi-AP capabilities element and/or amulti-AP request element, and if the probe request is not addressed tothe SSID and/or the virtual BSSID that represents the entire Multi-APset SS, the AP may respond with a Probe Response frame that may includea Multi-AP element. The Multi-AP element may include all informationregarding the multiple APs in the same set, which may include one ormore of the following: Virtual BSSID, SSID, Multi-AP beacon schedule,and/or Preferred Scanning methods. The above-mentioned information whichmay be included in the multi-AP element will be further described asfollows.

The virtual BSSID may represent the entire multi-STA set SS. The VirtualBSSID may be used by the STA to send a Probe Request or Authenticationor Association Request in order to get information or conductauthentication and/or association with the Multi-STA set SS.

The SSID may represent the entire multi-STA set SS. The SSID may be usedby the STA to send a Probe Request or Authentication or AssociationRequest in order to get information or conduct authentication and/orassociation with the Multi-STA set SS.

The Multi-AP beacon schedule may indicate the schedule at which beaconsor multi-AP beacons, FILS discovery frames, Probe responses, may betransmitted concurrently or sequentially by one or more APs within themulti-AP set SS. The multi-AP beacon schedule may be in terms of offsetthat references to the TSF timer which may also be included in the proberesponse, or that references to the end of the current frame. It mayalso be the schedule of triggered multi-AP beacon and/or multi-AP proberesponse, or FILS discovery frames.

Preferred Scanning methods may indicate the preferred method forscanning, including multi-AP active scanning, passive scanning, singleAP active scanning, etc.

It should be noted that those above-mentioned information which may beincluded in the multi-AP element is only given by way of example, and itis not intended to be exclusive or be limiting to the presentapplication. Any other available information may be included as long asit may follow the above-discussed principle and guideline.

If the Probe Request includes a multi-AP capabilities element and/or amulti-AP request element and the probe request is addressed to the SSIDand/or the virtual BSSID that represents the entire Multi-AP set SS, theAP may respond with a Probe Response frame or a trigger frame, e.g., asfollows.

If the AP responds with a Probe Response frame, the Probe Response framemay include a Multi-AP element. The Multi-AP element may include allinformation regarding the multiple APs in the same set, which mayinclude one or more of the following information as described before. Itmay subsequently trigger one or more probe response or beacon framestransmitted by one or more of APs in the same Multi-AP set SS.Additionally or alternatively, the AP may trigger a concurrenttransmission of a Multi-AP beacon or multi-AP probe responses frame thatmay be addressed to the probing STA, or to a broadcast address. Thetriggering of concurrent or sequential Multi-AP beacon and/or proberesponses may be following the multi-AP beacons schedule. If the APresponds with a trigger frame to one or more APs in the same multi-APset, the AP may trigger a concurrent transmission of a Multi-AP beaconor multi-AP probe responses frame that may be addressed to the probingSTA, or to a broadcast address. The triggering of concurrent orsequential Multi-AP beacon and/or probe responses may follow themulti-AP beacon schedule. The Multi-AP beacon or Multi-AP probe responseframe may be shared by the master AP to all other APs in the sameMulti-AP set SS. It should be noted that the above-mentioned ways toresponse with a Probe Response frame or a trigger frame are only givenby way of example, and they are not intended to be exclusive or belimiting to the present application. Any other available way may be usedas long as they may follow the above-discussed principle and guidelineof this application.

The STA, after receiving a Probe Response frame which may include amulti-AP element, may follow an instruction included in the ProbeResponse frame to conduct further scanning and/orauthentication/association. For example, if the Preferred ScanningMethod is indicated as Multi-AP Active scanning, the STA may send aProbe Request to the SSID and/or virtual BSSID representing the Multi-APset SS, which may also include Multi-AP element and/or Multi-AP requestelement. If the Preferred Scanning Method is indicated as passivescanning, the STA may follow the multi-AP beacon schedule to receive theone or more beacons, probe responses, FILS discovery frame, and/ortriggered beacons, probe responses and FILS discovery frames. If thePreferred Scanning Method is indicated as single-AP active scanning, theSTA may send a probe/authentication/association request to one or moreAPs that are included in Probe Response frames, or pre-acquiredinformation.

The following technical solution is directed to solve theabove-mentioned problems 1 and 2. Some embodiments disclosed belowinclude a multi-AP beacon. The multi-AP repetition beacon frame may betransmitted from a group of APs. In some embodiments, it is assumed thatmultiple APs may group together, and that backhaul connections areavailable among the multiple APs. In some embodiments, the multiple APsor the AP group may form a virtual AP, and the APs may share a commonvirtual BSSID (vBSSI) and/or virtual SSID (vSSID) when they transmit themulti-AP repetition beacon frames. In some embodiments, the multiple APsmay form a group, and a master AP may control the group, or a centralcontroller may control the group. The group of APs may transmit themulti-AP repetition beacon using a common BSSID assigned by the masterAP or a Multi-AP central controller.

The multi-AP repetition beacons transmitted from the group of APs mayhave the same MAC body and modulation and coding schemes, such that aSTA may combine the received signal. An indicator may indicate therepetition transmission such that the receiver may combine them. Forexample, a multi-AP repetition transmission field may be set, e.g., in aPLOP header, or MAC header or beacon frame, such that receiving STAs maycombine the received signal.

Multiple embodiments regarding the multi-AP beacon transmission areshown in FIGS. 10-14. The following description will describe each ofthese embodiments in detail.

FIG. 10 illustrates multi-AP repetition beacons transmitted sequentiallyin different time slots. In this example, each AP may still transmit itsown Beacon for its BSS, which is shown as a normal Beacon in the figure,so that the STAs may choose to associate with those individual APs firstand, depending on their capability to support Multi-AP transmission, maydecide whether or not to associate with the multi-AP group later. Asshown in FIG. 10, AP1 may transmit normal beacon B1; AP2 may transmitnormal beacon B2; AP3 may transmit normal beacon B3 and AP4 may transmitnormal beacon B4. The multi-AP repetition beacons (B shown in FIG. 10)may be transmitted sequentially by the group of APs.

In some embodiments, a leading AP may start the multi-AP repetitionbeacon transmission. The rest of APs in the group may follow xIFS (anyinter-frame spacing, e.g., short IFS (SIFS), point coordination function(PCF) IFS (PIFS), distributed coordination function (DCF) IFS (DIFS),etc.). The transmission order may be negotiated when the AP join thegroup. Alternatively, the transmission order may be determined bygeometry location of the APs, MAC addresses, time to join the group etc.

FIG. 11 illustrates multi-AP repetition beacons transmittedconcurrently. In this example, each AP may still transmit its own normalbeacon for its BSS sequentially, which is shown as a normal beacon(e.g., B1, B2, B3, and B4) in FIG. 11. The multi-AP repetition beacons(B shown in FIG. 11) may be transmitted concurrently by the group ofAPs. The transitions of the multi-AP repetition beacons may be exactlythe same and well synchronized so that STAs may be able to decode them.

FIG. 12 illustrates another approach, where the leading AP (e.g., AP1)may start the multi-AP repetition beacon transmission first. The rest ofthe APs in the group may transmit the multi-AP repetition beacon framesconcurrently an xIFS duration after reception of the leading APtransmission. In this method, the leading AP transmission may beconsidered as a trigger frame to trigger the multi-AP concurrent beacontransmission. In this approach, the APs in the group may transmit theirown normal beacons (e.g., B1, B2, B3 and B4) sequentially as shown inFIG. 12.

FIG. 13 illustrates another example approach, where the leading AP(e.g., AP1) may transmit a multi-AP beacon trigger frame (i.e., T shownin FIG. 13). All the APs in the group may transmit multi-AP repetitionbeacon frames concurrently an xIFS duration right after the triggerframe.

The multi-AP repetition beacons may be transmitted over multiplechannels if those channels may be idle. Both sequential and concurrenttransmission may be generalized to multiple channel transmission case.FIG. 14 illustrates an example of such sequential transmission scheme.As shown in FIG. 14, each AP may still transmit its own normal beaconfor its BSS, which may be shown as normal beacon in FIG. 14, i.e., B11,B12, B21, B22, B31, B32, B41, and B42. The multi-AP repetition beaconsmay be transmitted sequentially on two channels in this example in anon-overlapping format. AP1 may transmit multi-AP repetition beacon overchannel 1 in the first time slot shown in FIGS. 14, and AP2 may transmitit over channel 2 in the first time slot. Similarly, AP3 and AP4transmit their multi-AP repetition beacons in the second time slot overchannel 1 and channel 2 respectively. Alternatively, the leading AP mayneed to transmit a frame right before the set of multi-AP repetitionbeacon transmissions to let the APs synchronize. The frame may be atrigger frame or a beacon frame. It should be noted that theabove-mentioned embodiment shown with reference to FIG. 14 is only givenby way of example, and it's not intended to be exclusive or be limitingto the present application. Multiple APs may transmit their multi-APrepetition beacons in any other different ways associated with differenttime slots and different channels. For example, AP1 may transmit itsmulti-AP repetition beacon over channel 1 in the second time slot, andAP2 may transmit its multi-AP repetition beacon over channel 2 in thesecond time slot, and accordingly, AP3 may transmit its multi-APrepetition beacon over channel 1 in the first time slot, and AP4 maytransmit its multi-AP repetition beacon over channel 2 in the first timeslot.

At the end of the association process, a STA may associate with onegroup of APs in one channel and associate with another group of APs inanother channel. Some of those APs in two groups may be physically thesame. STAs may need to report back to the network about which APs theycan hear on which channel. The network then can complete the associationprocess using available resources, including physical APs and channels.

In some such methods, it may be assumed that each of the group of APs isavailable to transmit beacons at the same time. In some such methods, itmay be assumed that the leading AP may transmit and reserve thechannel(s), and the rest of APs may follow the transmission an xIFSduration after.

In cases where not all APs in the group are available to transmit eithersequentially or concurrently, e.g., due to hidden nodes or untruncatedtransmissions, an approach, such as the one illustrated in FIG. 15, maybe applied. As shown in FIG. 15, a repetition beacon transmissioninterval may be predefined or predetermined and known by STAs and APs.All the APs in the group may transmit multi-AP repetition beacons withinthe repetition beacon transmission interval once they may be available.In some embodiments, the APs in the group may not transmit a traditionalbeacon (their own beacon) in the interval. The repetition beacontransmission interval may be defined in one or more methods, such as astatic method, a semi-static method, and/or a dynamic method. Thesethree methods will be described with reference to detailed embodiment asfollows.

In a static method, the repetition beacon transmission interval may bedefined with fixed starting location and duration. The starting locationand duration of the interval may be predefined or predetermined, orannounced in previous multi-AP repetition beacons. In an embodiment, theduration may be defined using a real time unit, such as a microsecond.In another embodiment, the duration may be defined as a fractional ofthe beacon interval. The beacon interval may be defined as the durationbetween two different sets of repetition beacons as shown in FIG. 15.

In a semi-static method, the repetition beacon transmission interval maybe defined with a fixed duration, but with a dynamic starting location.That is, a starting location when an AP may transmit its first frame inmulti-AP repetition beacon transmission sequences may not be a fixedlocation. The AP may be a leading AP. The first frame may be a beaconframe or a trigger frame. The duration of the repetition beacontransmission interval may be predefined or predetermined, or announcedin previous multi-AP repetition beacons.

In a dynamic method, the repetition beacon transmission interval may bedefined as having both a dynamic starting location and a dynamicduration. The starting location may be the time when an AP transmits itsfirst frame in multi-AP repetition beacon transmission sequences. Theinterval duration may be adjustable due to density of the STAs in theBSS(s) or the virtual BSS. For example, in a densely deployed system,more transmissions and hidden nodes may be expected and a longerinterval may be beneficial. Otherwise, a shorter interval may be used.The duration of the interval may be announced in previous multi-APrepetition beacons. In cases where no duration is explicitly signaled,STAs and APs may reuse the same duration.

It should be noted that the above-mentioned three exemplary methods todefine the repetition beacon transmission interval are only given by wayof example, and they are not intended to be exclusive or be limiting tothe present application. There might be other available methods todefine the repetition beacon transmission interval as long as thosemethods follow the principle and guideline discussed above.

A STA may expect to receive repetition beacons within a time interval.In some implementations, the time interval may bepredefined/predetermined/signaled by the AP. In some implementations,the time interval may be determined based on a STA procedure. The timeinterval may be defined as having a starting location (t0) and duration(T). The duration may be determined, e.g., using previously receivedrepetition beacons or predefined, e.g., by a standard. The startinglocation may be determined, e.g., by previously received repetitionbeacons or predefined by standard in fixed location cases. In a dynamicstarting location case, the starting location may be determined when theSTA detects the first frame of the repetition beacon transmissions. Forexample, in dynamic starting location cases, the STA may haveencountered a chance to mis-detect the starting location (e.g., t1). TheSTA may then monitor the repetition beacon transmission interval frommis-detected starting location [t1, t1+T].

The STA may start a repetition beacon timer at the starting location t0.If the timer is less than duration T, the STA may continue monitoringthe channel(s) for repetition beacon transmissions. The STA may detect aframe transmission. By checking the PLOP header or control trailer orother type of separately encoded part of the frame, the STA may obtain atransmitter identity, such as MAC address, compressed MAC address,BSSID, compressed BSSID, BSS color, etc. The STA may recognize that thismay be a repetition transmission or HARQ transmission, e.g., bydetecting a repetition transmission field set to 1. If this is the firstframe within the interval from the same transmitter ID, the STA maydecode it. If decoding fails, the STA may save it in the buffer. If thisis not the first frame from the same transmitter ID, the STA may combineit with the data saved in the buffer. If it is not successfully decoded,the STA may save the combined data in the buffer and continue monitoringthe channel(s). If the timer is greater than duration T, the STA mayclear the buffer.

STAs, which may be associated with the BSSID carried by multi-APrepetition beacon, may be considered as STAs that may communicate withthe group of APs or the virtual AP. In a repetition beacon transmission,the AP group or the virtual AP may choose a modulation and coding scheme(MCS) which may be supported by all of the STAs. The MCS selected may behigher than the lowest MCS supported. While various approaches hereinare discussed with respect to repetition beacon transmission schemes,similar ideas may be applied to probe response frame and associationresponse frame transmissions. Information elements and fields have beendiscussed in other embodiments. It is noted that in each of the FIGS.10-14, each AP in the group may transmit one multi-AP repetition beaconin a beacon interval. However, this may be easily extended to a generalcase where each AP may be allowed to transmit 0 to N repetition beaconsin a beacon interval. In an example case, the AP group may contain onlyone AP, and the AP may still transmit multiple repetition beacons in abeacon interval. It is noted that the terms repetition beacon, multi-APrepetition beacon, and multi-AP beacon may be used interchangeably. InFIGS. 10-14, Beacon frames may be used to demonstrate the repetitiontransmission from multiple APs. The schemes may be easily extended byusing other control/management/data frames. For example, Beacon framemay be replaced by sounding frames, high reliable data transmissionframes etc.

The following technical solution is directed to solve theabove-mentioned problems 3. Some embodiments address a TSF for therepetition beacon. Some such embodiments may address timesynchronization issues when receiving from multiple AP. In this example,it is assumed that APs in a virtual AP set have their TSF synchronized,and that a multi-AP repetition beacon transmission procedure is used.

In some embodiments, the TSF can be signaled in the preamble of eachbeacon, such that each repetition has its own self-contained TSF timer.The timestamp field may be 8 bytes, which may increase the preamblesize. The increased size may reduce the range and reliability of thepreamble, preventing repetition beacon from being detected by a celledge STA. Accordingly, in some embodiments, signal target beacontransmission time (TBTT) is in the beacon frame instead of the timestampof the beacon. The preamble is used to signal the time offset betweenthe repetition beacon and the TBTT. In this approach, the preamble ofrepetition beacon_i, may provide the receiver with an offset betweenTBTT and the time of the beacon_i, as t_i. After single or combiningmultiple repetition beacons, the content of the beacon is decoded, andvalue of TBTT is known to the receiver. Based on t_i and receiversinternal clock at the time of receiving beacon_i, the receiver will beable to map TBTT to its own internal clock.

Some such embodiments have the advantage that every repetition beacon inthe same BI has the same TBTT value in the payload, and accordingly,repetition beacons can be combined (e.g., like HARQ transmissions).Furthermore, the repetition beacons of the same BI must finishtransmission within a beacon window after the TBTT, so the range of t_iis bounded by the beacon window or repetition beacon transmissioninterval defined in the above paragraphs regarding the multi-AP beacon.This window may be smaller than the range of Timestamp value.Accordingly, offset t_i may be more suitable to be carried in thepreamble of each repetition beacon. The t_i may be conceptualized as theleast significant bits (LSBs) or most significant bits (MSBs) of the 64bit Timestamp of each repetition beacon. For example, if the beaconwindow is 10 ms, an example t_i may be roughly the 14 LSB of theTimestamp. FIG. 16 illustrates an example TBTT/beacon window and t_i. Itshould be noted that the above-mentioned beacon window and Timestamp areonly given by way of example, and they are not intended to be exclusiveor be limiting to the present application.

Some embodiments include further optimization to further reduce theinformation representing t_i. In some embodiments, t_i is quantized witha granularity of Δt. For example, if Δt=64 us, and a beacon window is 10ms, then Li can be represented by 8 bits in the preamble. This mayproduce an ambiguity (e.g., a 64 us ambiguity in this example). Oneapproach to resolving this ambiguity is to mandate AP to always start orend the repetition beacon transmission at the boundary of Δt interval,and t_i indicates the time from TBTT to the start or the end of therepetition beacon. Starting or ending at Δt interval each presentvarious challenges.

Starting at the boundary may limit the channel access opportunity, e.g.,because the boundary may coincide with a medium busy period, whilenon-boundary duration coincides with the medium idle time. To increasethe channel access opportunity, in some embodiments, a reservationsignal may be used. For example, reservation signals (or dummy signals)may be inserted before (e.g., immediately before) the real beacontransmission such that the channel is occupied. The real beacontransmission may start from the boundary of Δt interval. However, thelength of the reservation signal may not be an integer multiple of OFDMsymbols. Similarly, ending at the boundary may require padding to beapplied, and the padding may not be an integer multiple of OFDM symbols.

FIG. 17 illustrates an example approach to resolving this ambiguity,while preserving the reservation/pad signal to be integer multiple ofOFDM symbols. These symbols can be used to carry extra parity bits ortraining fields to protect the PPDU, unlike an arbitrary length busysignal which cannot be utilized by the receiver.

As shown in FIG. 17, the pad is shown at the end of the PPDU.Alternatively, the pad may be placed at the beginning of the PPDU to beused as a reservation signal. Alternatively, the pad may be placed in apre-defined location in a PPDU. The pad may be used to make the end (orstart) of the PPDU be within 1 OFDM symbol at the nearest Δt intervalboundary. In some embodiments, the PPDU length signalled in the preambleis the length to the end of pad. The extra information in the pad mayinclude additional parity bits or training symbols. In some embodiments,the PPDU length signalled in the preamble is the length to the end ofpad, but there is no signal actually transmitted in pad.

To resolve the ambiguity within an OFDM symbol, one or more pairs ofshort training field (STF) or long training field (LTF) symbols can beused, e.g., one without any phase adjustment, the other having a linearphase shift corresponding to the time offset between the end of padsymbol and the nearest Δt interval boundary. Based on the linear phaseshift difference between the two symbols, the receiver may determine thetime of the nearest Δt interval boundary, from the end time of the pad.From the time of the nearest Δt interval boundary, the receiver may usea quantized t_i (which is an integer multiple of Δt, 4Δt in the examplebelow) from the preamble to derive TBTT. In some embodiments, the padduration is fixed and can be one or more pairs of special and/or longerLTF, which has T_sym=Δt. In this case, the PPDU may no longer need to bepadded with an integer number of normal OFDM symbols to the closet Δtinterval boundary. This may enable a direct estimation of packetstart/end time to the nearest Δt interval boundary. In variousembodiments, some of the time related parameters, such as offset t_i,quantized t_i, are included in preamble. Alternatively, they may beincluded in any other separately encoded and CRC protected part.

The following technical solution is directed to solve theabove-mentioned problem 4. Some embodiments address multi-AP spatialpuncturing transmission. In some embodiments, multi-AP transmission andreception may involve a group of APs transmitting to and receiving fromSTAs. In other embodiments, multiple APs may form a group of APs or avirtual AP to communicate with STAs. It may not be necessary for all APsin the group to join a particular transmission to or reception from aSTA, or it may not be efficient to use all of the APs in the group tocommunicate with a STA. In some implementations, the STA may facilitatethe group of APs in a dynamic AP selection scheme (e.g., a multi-APspatial puncturing transmission scheme) such that only a subset of theAPs is utilized. In other words, a multi-AP spatial puncturingtransmission scheme may be used, e.g., to enable a subset of APs in thegroup to transmit to and/or receive from a STA. In that case, a STA maycommunicate with a subset of APs and the rest of APs in the group may beconsidered as punctured. That is, some APs in the group which will notcommunicate with the STA may be considered as ‘punctured’ from thecommunication in the spatial domain.

To enable spatial puncturing transmission, the AP group or the virtualAP may determine the subset of APs to use for communication with theSTA. In some embodiments, a modified multi-AP repetition beacontransmission scheme is used for the STA to measure the received signalpower from each AP, and provide feedback to the AP group or the virtualAP. The following description will describe such multi-AP repetitionbeacon transmission scheme according to preferred embodiments of thisapplication with reference to FIG. 18 and FIG. 19. Note, we use multi-APrepetition beacon transmission scheme as example. It may be extended tomulti-AP repetition transmission schemes by using any other frames, suchas management frames, control frames or data frames, instead of beaconframes.

FIG. 18 illustrates overall processes of a multi-AP repetition beacontransmission scheme according to an embodiment of this application. Asshown in FIG. 18, it is assumed that AP1, AP2, AP3 and AP4 coordinate toform a multi-AP transmission/reception group or multi-AP transmissionset or a virtual AP. Each of the APs may transmit a repetition beaconincluding both a common information part (i.e., a common part shown inFIG. 18) and an AP-specific information part (i.e., a specific partshown in FIG. 18). Therefore, as shown in FIG. 18, there are four commoninformation parts in total, and four AP-specific information parts intotal. The common information parts are transmitted, or assumed to betransmitted (and received) from multiple APs and may be identical toenable combining and decoding at the STA. The AP-specific informationparts that may be transmitted (and received) differ from AP to AP toenable the STA to identify a specific AP transmitting the AP-specificinformation part or perform AP specific measurements (discussed below).Based on the decoding of the common information parts and theAP-specific information parts, the STA may provide feedback informationto the multi-AP transmission set (i.e., the multi-AP group) to assistfuture multi-AP transmissions; e.g., AP and STA selection, multi-APscheme, MCS, power etc. The common information part and the AP-specificinformation parts may be separately encoded and protected usingdifferent CRCs.

It should be noted that the FIG. 18 only illustrates overall processesof an exemplary multi-AP repetition beacon transmission scheme, and itsdetailed embodiments will be described below with reference to FIG. 19.In this application, unless otherwise indicated, the terms “commoninformation part” and “common part” may be used interchangeably, and theterms “AP-specific information part” and “AP-specific part” may be usedinterchangeably.

It should be noted that in some embodiments, the common information partmay also be referred to as “common beacon” and the AP-specificinformation part may also be referred to as “AP-specific beacon”. Therepetition beacon may actually be transmitted by two separate parts: oneis used for common information part, and another is used for AP-specificinformation part. For example, in a scenario, the common informationpart and the AP-specific information part may be transmitted separately.In that case, the common information part may be referred to as “commonbeacon”, and the AP-specific information part may be referred to as“AP-specific beacon.”

Preferably, in each repetition beacon, the common information part andthe AP-specific information part may be transmitted together with aninterframe spacing between them. In that case, the common informationpart may also be referred to as “common beacon”, and the AP-specificinformation part may also be referred to as “AP-specific beacon.”Therefore, the terms which could be used for different parts (i.e., thecommon part and the AP-specific part) of the repetition beacon may varyaccording to different embodiments.

FIG. 19 illustrates a flow chart of a method 1900 for multi-APtransmission according to this application. As shown in FIG. 19, themethod 1900 comprises: at 1901, receiving a plurality of repetitionbeacons, one from each of a plurality of APs, each of the plurality ofrepetition beacons comprising a common information part and anAP-specific information part; at 1902, decoding at least one of theplurality of common information parts or a combination of one or morecommon information parts to obtain a first parameter; at 1903, decodingthe plurality of AP-specific information parts to obtain a plurality ofsecond parameters, each associated with one of the plurality of APs; at1904, generating feedback based on the first parameter, the plurality ofsecond parameters and a number of the plurality of APs; and at 1905,transmitting the feedback to at least one of the plurality of APs.

Accordingly, the WTRU according to this application may comprises: atransceiver, configured to receive a plurality of repetition beacons,one from each of a plurality of APs, each of the plurality of repetitionbeacons comprising a common information part and an AP-specificinformation part; and a processor, configured to decode at least one ofthe plurality of common information parts or a combination of one ormore common information parts to obtain a first parameter; decode theplurality of AP-specific information parts to obtain a plurality ofsecond parameters, each associated with one of the plurality of APs; andgenerate feedback based on the first parameter, the plurality of secondparameters and a number of the plurality of APs, wherein the transceiveris further configured to transmit the feedback to at least one of theplurality of APs.

The following description will describe the above-mentioned processesfrom 1901 to 1905 and the components of the WTRU in detail. Someembodiments may also direct to the example shown in FIG. 18 forreference.

The process at 1901 will be discussed as follows. As shown in FIG. 19,the method 1900 may comprise, at 1901, receiving a plurality ofrepetition beacons, one from each of a plurality of APs, each of theplurality of repetition beacons comprising a common information part andan AP-specific information part. Accordingly, the transceiver may beconfigured to receive a plurality of repetition beacons, one from eachof a plurality of APs, each of the plurality of repetition beaconscomprising a common information part and an AP-specific informationpart.

The repetition beacon may also be referred to as multi-AP repetitionbeacon or multi-AP repetition beacon frame. As discussed above withreference to FIG. 10-14, the multi-AP repetition beacon may betransmitted from a group of APs. In some embodiments, the multiple APsor the AP group may form a virtual AP, and the APs may share a commonvirtual BSSID (vBSSI) and/or virtual SSID (vSSID) and/or virtual BSScolor when they transmit the multi-AP repetition beacon frames. In someembodiments, the multiple APs may form a group, and a master AP maycontrol the group or a central controller may control the group. Thegroup of APs may transmit Multi-AP repetition beacon with using a commonBSSID assigned by the master AP or a Multi-AP central controller.

The multi-AP repetition beacons may be transmitted in different waysshown in FIGS. 10-14. For example, the multi-AP repetition beacons maybe transmitted in different time slot sequentially as shown in FIG. 10.The multi-AP repetition beacons may be transmitted concurrently as shownin FIG. 11. In an embodiment shown in FIG. 12, a leading AP may startthe multi-AP repetition beacon transmission first, and the rest of APsin the group may transmit the multi-AP repetition beacon concurrentlyxIFS duration after reception of the leading AP transmission. In anembodiment shown in FIG. 13, a leading AP may transmit a multi-AP beacontrigger frame, and then all APs in the group may transmit multi-APrepetition beacon concurrently xIFS duration right after the triggerframe.

The multi-AP repetition beacons transmitted from the group of APs mayhave the common information part comprising MAC body and modulation andcoding schemes so that a STA may combine the received signal. A specialindicator may be needed to indicate the repetition transmission so thereceiver may combine them. For example, in PLOP header, or MAC header orbeacon frame, a special indicator, such as a multi-AP repetitiontransmission field, may be set so that a receiving STA may combine them.

In some embodiments, the common information part may comprise identicalinformation among the group of APs. For example, the common beacon maycarry information discussed above, such as Virtual BSSID, SSID, multi-APbeacon schedule, preferred Scanning methods, members of the samemulti-AP group, and other information normally carried in Beacon frame.The information carried by the common beacon can be understood withreference to the above paragraphs regarding the multi-AP scanningscheme. It should be noted the above-mentioned information in the commoninformation part is only given by way of example, and they are notintended to be exclusive or be limiting to the present application. Thecommon information part may comprise any available information based onthe above described principle of this application as long as thatinformation may be helpful to realize such principle.

The AP-specific information part may comprise one or more of thefollowing fields: a field for AP ID, a field for a total number ofrepetition beacons, a field for a repetition transmission ID, a decodingparameter (e.g., a decoding metric) and/or a field for a number ofremaining repetition beacons to be transmitted. The AP ID field may beused to uniquely identify an AP in the AP group/virtual AP. The totalnumber of repetition beacons field may be used to indicate the number ofthe total number of repetition beacons. Alternatively, this may becarried in the common beacon part. The Repetition transmission ID fieldmay be set to k to indicate the current transmission may be the kthrepetition transmission among the beacon set. It should be noted thatthe above-mentioned fields in the specific information part is onlygiven by way of example, and they are not intended to be exclusive or belimiting to the present application. The AP-specific information partmay comprise any available information/field based on the abovedescribed principle of this application as long as thatinformation/field may be helpful to realize such principle.

The common information part and the AP-specific information part may berealized and transmitted using multiple different ways. The followingdescription will discuss some preferred ways for realizing andtransmitting the common information part and the AP-specific informationpart.

In some embodiments, the repetition beacon (i.e., the multi-APrepetition beacon) may be aggregated with the normal 802.11 beacon,e.g., with each beacon being sent in a coordinated manner at a TBTT foreach AP. In that case, the common information part and the AP-specificinformation part may be aggregated with the normal beacon.

In some embodiments, the repetition beacon may be sent as a separatebeacon with common and AP-specific components, i.e., the commoninformation part and the AP-specific information part. Preferably, thecommon information part and the AP-specific information part may betransmitted in the ways shown in FIGS. 10-25). The following descriptionwill further discuss those ways with reference to FIGS. 10-25.

Preferably, in each repetition beacon, the common information part andthe AP-specific information part may be aggregated together with nointerframe spacing between them. This preferable embodiment may beimplemented through the following four different scenarios shown by fourelements in FIG. 20.

In the first scenario, the common information part and the AP-specificinformation part may be transmitted with separate preambles as anaggregated PPDU (A-PPDU). As shown in the first element of FIG. 20, acommon information part 2003 may be transmitted with a legacy preamble2001 and an EHT preamble 2002; an AP-specific information part 2006 maybe transmitted with a legacy preamble 2004 and an EHT preamble 2005.There is no interframe spacing between the common information part 2003and the AP-specific information part 2006. The sequence of the commoninformation part and the AP-specific information part shown by the firstelement is only exemplary. For example, in an embodiment, the item 2003may represent an AP-specific information part and meanwhile the item2006 may represent a common information part. It should be noted thatthe first element of FIG. 20 is only given by way of example, and it isnot intended to be exclusive or be limiting to the present application.For example, the common information part and the AP-specific informationpart may be transmitted with HE/EHT or a later version preamble.

In the second scenario, they may be transmitted with a single legacypreamble but with separate EHT preambles. As shown in the second elementof FIG. 20, a common information part 2013 may be transmitted with anEHT preamble 2012; an AP-specific information part 2015 may betransmitted with an EHT preamble 2014; the common information part 2013and the AP-specific information part may be transmitted with a legacypreamble 2011. There is no interframe spacing between the commoninformation part 2013 and the AP-specific information part 2015. Thesequence of the common information part and the AP-specific informationpart shown by the second element is only exemplary. For example, in anembodiment, the item 2013 may represent an AP-specific information partand meanwhile the item 2015 may represent a common information part. Itshould be noted that the second element of FIG. 20 is only given by wayof example, and it is not intended to be exclusive or be limiting to thepresent application. For example, the common information part and theAP-specific information part may be transmitted with HE/EHT or a laterversion preamble.

In the third scenario, the AP-specific information may be transmitted asa control trailer to the common AP. As shown in the third element ofFIG. 20, the AP-specific information part may be carried in a controltrailer 2024. A common information part 2023 and the AP-specificinformation part 2024 may be transmitted with a legacy preamble 2021 andan EHT preamble 2022. There is no interframe spacing between the commoninformation part 2023 and the AP-specific control trailer 2024. Thesequence of the common information part and the AP-specific informationpart shown by the third element is only exemplary. For example, in anembodiment, the item 2023 may represent an AP-specific information partand meanwhile the item 2024 may represent a control trailer whichcarries a common information part. It should be noted that the thirdelement of FIG. 20 is only given by way of example, and it is notintended to be exclusive or be limiting to the present application. Forexample, the common information part and the AP-specific informationpart may be transmitted with HE/EHT or a later version preamble.

In the fourth scenario, the AP-specific information part may be placedin a specific area in the PLOP header. As shown in the fourth element ofFIG. 20, the AP-specific information part may be an AP-specific header2033. In that case, a common information part 2034 and the AP-specificheader maybe transmitted with a legacy preamble 2031 and an EHT preamble2032. The sequence of the common information part and the AP-specificinformation part shown by the fourth element is only exemplary. Forexample, in an embodiment, the item 2033 may represent a common headeras a common information part and meanwhile the item 2034 may representan AP-specific information part.

The above description discussed a separation between the commoninformation part and the AP-specific information part. It should benoted that such separation may be necessary to enable the STA toperform, on the common preamble, repetition, combining, etc. It shouldbe also noted that the preamble for the AP-specific part may havedifferent transmission parameters (e.g. MCS) from the preamble for thecommon information part. For example, the AP-specific information partmay be coded and modulated with lower data rate so that a STA may beable to decode this part without repetition combination as did for thecommon information part.

Preferably, the common information part and the AP-specific informationpart may be transmitted together with an xIFS between them. In suchcases, the common information part and the AP-specific information parthave to have separate preambles. FIG. 21 illustrates an exemplaryseparated structure for this preferably embodiment. As shown in FIG. 21,a common information part 2103 may be transmitted with a legacy preamble2101 and an EHT preamble; an AP-specific information part 2106 may betransmitted with a legacy preamble 2104 and an EHT preamble 2105; thereis an xIFS spacing between the common information part 2103 and thelegacy preamble 2104. The sequence of the common information part andthe AP-specific information part shown in FIG. 21 is only exemplary. Forexample, in an embodiment, the item 2103 may represent an AP-specificinformation part and meanwhile the item 2106 may represent a commoninformation part. For example, the common information part and theAP-specific information part may be transmitted with HE/EHT or a laterversion preamble.

Preferably, the common information part and the AP-specific part may betransmitted separately as two different beacons. That is, the commoninformation part may be transmitted as a common beacon, and theAP-specific part may be transmitted as an AP-specific beacon. In thatcase, each AP may transmit a common beacon and an AP-specific beacon,and the common beacon and the AP-specific beacon together may form arepetition beacon.

In some embodiments, the common beacon and the AP-specific beacon may betransmitted separately with different TBTTs.

In some embodiments, the common beacons are grouped together and the APspecific beacons are grouped together. The STA may implicitly identifythe AP that sends a common beacon based on its transmission timerelative to the transmission of the AP-specific beacon. Some suchembodiments allow the use of the normal beacon as the AP specificbeacon. The order of the beacons may be signaled in the common beaconand the order may be static, semi-static or dynamic.

In some embodiments, it may be necessary to coordinate the transmissionsof the repetition beacons, as the APs may be located in a manner thatenhanced distributed channel access (EDCA) does not prevent them fromtransmitting at the same time while the STA needs them to transmit atseparate times to be able to decode the AP-specific parts of therepetition beacons. To ensure that the AP-specific parts of therepetition beacons do not overlap, a transmission window may be definedand an AP is allowed to transmit according to its window (e.g., eithertransmitting within its window only, or not transmitting within itswindow). Thus, by not letting multiple windows overlap with each other,the APs may coordinate to ensure that their repetition beacons do notoverlap. Therefore, both the common parts and the AP-specific parts fromthe repetition beacons may be decoded successfully. FIGS. 22-23 show twoexamples of the above-mentioned windows. The following description willdescribe the windows with reference to each example in more detail.

FIG. 22 illustrates an example of the above-mentioned windows. In thisexample, each AP is allowed to transmit a repetition beacon within awindow assigned to it only. As shown in FIG. 22, B1 represents arepetition beacon transmitted by AP1, and AP1 may only transmit itsrepetition beacon within a B1 window 2201. B2 represents a repetitionbeacon transmitted by AP2, and AP2 may only transmit its repetitionbeacon within a B2 window 2202. B3 represents a repetition beacontransmitted by AP3, and AP3 may only transmit its repetition beaconwithin a B3 window 2203. B4 represents a repetition beacon transmittedby AP4, and AP4 may only transmit its repetition beacon within a B4window 2204.

As shown in FIG. 22, the B1 window 2201, the B2 window 2202, the B3window 2203 and the B4 window 2204 may not overlap with each other. Inone embodiment, there may be no time gap between two adjacent windows.In other words, the windows assigned to different APs may connect toeach other end to end. For example, as shown in FIG. 22, there is notime gap between the B1 window 2201 and the B2 window 2202. The restwindows may be designed in a similar fashion. As shown in FIG. 22, AP1may only transmit a second repetition beacon (represented by 2205) afterthe B4 window 2204. That is, the time duration (e.g., TBTT) between twosuccessive windows assigned for AP1 may be greater than the length ofthe windows assigned for AP2, AP3 and AP4.

In another embodiment, there may be a time gap between two adjacentwindows. For example, there may be a time duration (not shown in FIG.22) between B1 window for AP1 and B2 window for AP2. The rest windowsmay be designed in a similar fashion. In that case, AP1 may onlytransmit a second repetition beacon after the B4 window. That is, thetime duration (e.g., TBTT) between two successive windows assigned forAP1 may be greater than the length of the windows assigned for the restAP in the group plus the time gaps between each two adjacent windows.

It will be appreciated that the above embodiments described and theexample shown in FIG. 22 are only given by way of example, and they arenot intended to be exclusive or be limiting to the present application.For example, there may be more than (or less than) 4 APs in the group,and windows for those APs may be designed in a similar way as discussedabove as long as those repetition beacons may be transmitted separatelywithout overlapping with each other.

FIG. 23 illustrates another example of the above-mentioned windows. Inthis example, each AP is allowed to transmit a repetition beacon withina window assigned to it only. As shown in FIG. 23, B1 represents arepetition beacon transmitted by AP1, and “No B1 Tx” represents a windowassigned for AP1. AP1 may not be allowed to transmit its repetitionbeacon within “No B1 Tx”. B2 represents a repetition beacon transmittedby AP2, and “No B2 Tx” represents a window assigned for AP2. AP2 may notbe allowed to transmit its repetition beacon within “No B2 Tx”. B3represents a repetition beacon transmitted by AP3, and “No B3 Tx”represents a window assigned for AP3. AP3 may not be allowed to transmitits repetition beacon within “No B3 Tx”. B4 represents a repetitionbeacon transmitted by AP4, and “No B4 Tx” represents a window assignedfor AP4. AP4 may not be allowed to transmit its repetition beacon within“No B4 Tx”.

As shown in FIG. 23, the repetition beacons (e.g., B1, B2, B3, and B4)may be transmitted separately without overlapping with each other.Meanwhile, the duration of the window “No B1 Tx” may be long enough tolet the rest APs (e.g., AP2, AP3 and AP4) complete their repetitionbeacon transmission. Further, the duration of the window “No B2 Tx” maybe long enough to let the rest APs (e.g., AP3 and AP4) complete theirrepetition beacon transmission. Moreover, the duration of the window “NoB3 Tx” may be long enough to let the rest APs (e.g., AP4) complete theirrepetition beacon transmission.

As shown in FIG. 23, the windows may share the same length. For example,the window “No B1 Tx” may have the same length as that of the window “NoB2 Tx”. As shown in FIG. 23, AP1 may only transmit a second repetitionbeacon (represented by 2301) after the window “No B4 Tx”. That is, thetime duration (e.g., TBTT) between two successive repetition beacontransmissions may be greater than the duration from the starting pointof the window “No B2 Tx” to the end point of the window “No B4 Tx”.

It will be appreciated that the above embodiments described and theexample shown in FIG. 23 are only given by way of example, and they arenot intended to be exclusive or be limiting to the present application.For example, there may be more than (or less than) 4 APs in the group,and windows for those APs may be designed in a similar way as discussedabove as long as those repetition beacons may be transmitted separatelywithout overlapping with each other. For another example, the windowsshown in FIG. 23 may not share the same length. In that case, AP1 mayonly transmit a second repetition beacon after the end point of thewindow “No B4 Tx”.

The process at 1902 will be discussed as follows. As shown in FIG. 19,at 1902, the method 1900 may comprise decoding at least one of theplurality of common information parts or a combination of one or morecommon information parts to obtain a first parameter. Accordingly, theprocessor is configured to decode at least one of the plurality ofcommon information parts or a combination of one or more commoninformation parts to obtain a first parameter.

As discussed above, the common information parts may comprise identicalinformation among the group of APs. Therefore, decoding a subset of thecommon information parts may obtain necessary information needed for theother processes following the process at 1902. In an embodiment,decoding only one common information part from all of the receivedcommon information parts may be good enough. For example, if thetransceiver received four common information parts from our APsrespectively and the four common information parts are identical, thenthe processor may only one common information part (anyone of the fourcommon information parts) to obtain the first parameter. In anotherembodiment, one or more of the received common information parts may bebuffered, combined and decoded in order to obtain the first parameter.For example, if the transceiver received a first common information partfrom AP1, a second common information part from AP2, and a third commoninformation part from AP3, then the processor may decode a combinationof the first common information part and the second common informationpart to obtain the first parameter. The processor may also decode acombination of all above-mentioned three common information parts toobtain the first parameter. The way to decode a combination of multiplecommon information parts will be further described below with referenceto a process to obtain a total number of the APs in the group.

Preferably, the process at 1902 may further comprise: buffering theplurality of common information parts; combining the plurality of commoninformation parts; and decoding the combined common information parts.Accordingly, for decoding at least one common information part to obtaina first parameter, the processor may be configured to buffer theplurality of common information parts, combine the plurality of commoninformation parts, and decode the combination of common informationparts.

The first parameter may indicate that the max number of APs which may beselected to do multi-AP transmission. Generally, the method 1900 mayreturn a feedback indicating desired AP combination(s) for multi-APtransmission to the AP group, and then the AP group may use thisfeedback to select an AP or multiple APs for multi-AP transmission.Therefore, the max number of APs which will be selected to do multi-APtransmission may also represent how many APs at most a desired APcombination may have. In other words, the first parameter may representhow many APs at most the STA may select to calculate in order to obtaindesired AP combination(s). For example, the first parameter may indicatethat the max number of APs which may be selected for multi-APtransmission is M. In other words, there may be at most M APs in adesired AP combination. Preferably, M is 2. That is, in a preferredembodiment, the first parameter may indicate that at most two AP in thegroup may be selected for multi-AP transmission. The first parametershould be no more than the total number of APs in the group. Thefollowing description will further describe this first parameter withreference to detail embodiments below. It should be noted that in thisapplication, unless otherwise indicated, the terms “an AP combination”and “a combination of AP(s)” may be used interchangeably.

The first parameter may indicate a preferred multi-AP scheme to be usedto enable the STA to do calculation at a later process, e.g., theprocess at 1904. The preferred multi-AP scheme may indicate a way ofestimate a decoding metric (e.g., a second parameter described later).It should be noted that the decoding metric may also be independent ofthe multi-AP scheme, and the manner of selecting APs by the AP group maybe implementation dependent. It should also be noted that the firstparameter may not be the only parameter obtained from the commoninformation parts. Other parameters may also be obtained from the commoninformation parts as long as they may help to realize the principle ofthis application. For example, a fourth parameter (described below) maybe obtained from a combination of one or more common information parts.

The process at 1903 will be discussed as follows. As shown in FIG. 19,at 1903, the method 1900 may comprise decoding the plurality ofAP-specific information parts to obtain a plurality of secondparameters, each associated with one of the plurality of APs.Accordingly, the processor may be configured to decode the plurality ofAP-specific information parts to obtain a plurality of secondparameters, each associated with one of the plurality of APs.

The STA may identify the specific APs by decoding the AP specificinformation. The second parameter may be a decoding metric which may beused to represent an AP's capability to support multi-AP transmissionwith the STA. Preferably, the second parameter may include any one ofthe following parameters: Signal to Noise Ratio (SNR), Signal toInterference and Noise Ratio (SINR), Reference Signal Received Power(RSRP), and Reference Signal Received Quality (RSRQ). Theabove-mentioned exemplary second parameter may be considered as anindicator for network quality. Therefore, the STA may do calculationbased on network quality, thereby providing a result of desired APcombination(s).

Although the above description already describes some examples of thesecond parameter, they are not intended to be exclusive or be limitingto the present application. The second parameter may also be any otherdecoding metrics or parameters as long as they may help to realize theprinciple of this application. The following description will furtherdescribe the second parameter with reference to detailed embodiments.

The process at 1904 will be discussed as follows. As shown in FIG. 19,at 1904, the method 1900 may comprise generating feedback based on thefirst parameter and the plurality of second parameters and the totalnumber of the plurality of APs. Accordingly, the processor may beconfigured to generate feedback based on the first parameter, theplurality of second parameters and a number of the plurality of APs.

The STA may obtain the total number of the APs in the group by decodingthe common information parts from the APs. For example, as shown in FIG.18, the STA (or the transceiver) may receive one packet or transmission(e.g., the common information part from AP1) and then the STA may try todecode the packet or transmission. If the STA fails to decode the packetor transmission, and the STA may know that more repetition transmissionsmay follow, the STA may buffer the received packet or transmission(e.g., log likelyhood ratios (LLRs) or received demodulated complexnumbers). Then, the receiver may continue receiving the followingrepetition transmissions, e.g., the common information part from AP2.Once the receiver receive a signal which may be a repetitiontransmission for the bufferred one, the STA may combine the receivedsignal (e.g., the common information part from AP2) with bufferredsignal (e.g., the common information part from AP1) and then decode. Ifthe STA fails to decode the combined signal, and STA may know that morerepetition transmissions are expected, the STA may buffer the updatedsignal (e.g., the combination of common information part from AP1 andAP2). And then, in a similar way, the STA may receive, buffer andcombine more signals (e.g., the common information parts from AP3 andAP4) until the STA successfully decodes a combined signals. In this way,the STA may know parameters (e.g., the above-mentioned first parameter)obtained from decoding the common information part(s). Also in this way,the processor may know the total number of the APs in the group. Forexample, if the processor bufferred, combined and decoded four commoninformation parts, then the processor may know the total number of APsin the group is 4. In one embodiment, the number of total repetitionsmay be in PHY layer signaling and decoded before decoding commoninformation part. In another embodiment, the processor may obtain thenumber of the APs in the group by decoding the received AP-specificinformation parts. For example, if the processor decoded 4 AP-specificinformation parts, the processor will know that the total number of APsin the group is 4.

It should be appreciated that the above-mentioned embodiments andexamples of the number of APs are only given by way of example, and theyare not intended to be exclusive or be limiting to the presentapplication. The number of APs in a group may be obtained through anyother available methods as long as they may help to realize theprinciple of this application.

Preferably, the process at 1904 may comprise the following twosub-processes: performing a calculation based on the first parameter,the plurality of second parameters and the number of the plurality ofAPs to obtain a calculation result; and generating the feedback based onthe calculation result.

The processor may perform the calculation based on the first parameter,the obtained second parameters (i.e., decoding metrics) and the numberof APs. After the calculation, one or more AP combinations may beobtained. Based on the above-mentioned first parameter, a desired APcombination may comprise M APs at most. Therefore, in each obtained APcombination, there may be only one AP or multiple APs (i.e., less thanor equal to M APs). The calculation may be mainly performed on thedecoding metrics, thereby obtaining new decoding metrics. In thisapplication, those new decoding metrics obtained from the calculationmay be referred to as third parameters. Preferably, the calculationresult may comprise one or multiple AP combinations. Preferably, thecalculation result may further comprise a third parameter for each ofthe plurality of AP combinations. The following description will furtherdescribe AP combinations as well as their third parameters withreference to detailed embodiments. In this method, the calculationmentioned above may be performed on the STA side and the STA mayfeedback suggested AP combination(s) to the APs.

In an embodiment, the processor may perform calculation by averaging thevalue of the second parameters of APs in each AP combination. In thisembodiment, the calculation may be performed based on the followingequation (1)

$\begin{matrix}{Z = \frac{x_{1} + x_{2} + \ldots + x_{n}}{n}} & {{Equation}\mspace{11mu} 1}\end{matrix}$

In the equation (1), x_(n) represents a second parameter value of an AP;n represents the number of APs in an AP combination; Z represents anaverage value of the APs' second parameter values in the AP combination.

In another embodiment, the processor may perform calculation bycalculating a difference between an average value of APs' secondparameter values in an AP combination and an overall average value ofall APs' second parameter values in the group. In this embodiment, thecalculation may be performed based on the following equation (2)

$\begin{matrix}{Z = {\frac{x_{1} + x_{2} + \ldots + x_{n}}{n} - \frac{x_{1} + x_{2} + \ldots + x_{m}}{m}}} & {{Equation}\mspace{11mu} 2}\end{matrix}$

In the equation (2), x_(n) and x_(m) represent a second parameter valueof an AP; n represents the number of APs in an AP combination; and mrepresents the total number of APs in the group.

The following description will describe the calculation performed by theSTA in detail with reference to three examples.

In a first example, there are following assumptions: the first parameter(M) is 2 indicating at most two APs in a desired AP combination; thetotal number of APs is 4; the second parameter is SINR value of each AP;the SINR value of AP1 is 6, the SINR value of AP2 is 12; the SINR valueof AP3 is 18; and the SINR value of AP4 is 24. It should be noted thatsince there are at most two APs in a desired AP combination, a desiredcombination may comprise only one AP or at most two AP. All potentialqualified AP combination should count. Based on the first parameter andthe number of APs, there are 4 ways to select a single AP from the fourAPs, and 6 ways to select two APs from the four APs (i.e., C₄²=(4×3)/(2×1)), i.e., a total of 10 different AP combinations: (1) AP1;(2) AP2; (3) AP3; (4) AP4; (5) AP1+AP2; (6) AP1+AP3; (7) AP1+AP4; (8)AP2+AP3; (9) AP2+AP4; and (10) AP3+AP4. For an AP combination comprisingtwo APs, the STA may obtain a SINR value for the AP combination byaveraging two SINR values of the two APs in the AP combination based onthe above equation (1). For example, the SINR value for the APcombination comprising AP2 and AP3 is 15. Therefore, after thecalculation discussed above, the STA may obtain the following Table 1.As shown in Table 1, those obtained SINR values shown in the second lineare third parameters for obtained AP combinations shown in the firstline.

TABLE 1 AP AP1 + AP1 + AP1 + AP2 + AP2 + AP3 + combination AP1 AP2 AP3AP4 AP2 AP3 AP4 AP3 AP4 AP4 SINR value 6 12 18 24 9 12 15 15 18 21 (dB)

As shown in Table 1, the calculation result comprises multiple APcombination shown in the first line and multiple SINR values (i.e.,third parameters) each of which corresponds to an AP combination.

In a second example, there are the same assumptions as those in theabove first example. That is, the first parameter is 2, indicating thereare at most two APs in a desired AP combination; the number of APs is 4;the second parameter is SINR value of each AP; the SINR value of AP1 is6, the SINR value of AP2 is 12; the SINR value of AP3 is 18; and theSINR value of AP4 is 24. The difference between the second example andthe first example is the way to perform calculation. In the secondexample, the STA may perform the calculation based on the above equation(2). After the calculation, the STA may obtain the following APcombinations with SINR values shown in Table 2.

TABLE 2 AP AP1 + AP1 + AP1 + AP2 + AP2 + AP3 + combination AP1 AP2 AP3AP4 AP2 AP3 AP4 AP3 AP4 AP4 SINR value −9 −3 3 9 −6 −3 0 0 3 6difference (dB)

In a third example, there are following assumptions: the first parameteris 3, indicating that there are at most three APs in a desired APcombination; and the other assumptions are the same as those in theabove first example. The STA may perform the calculation based on theabove equation (1). After the calculation, the STA may obtain thefollowing AP combinations with SINR values shown in Table 3.

TABLE 3 AP1 + AP1 + AP1 + AP2 + AP2 + AP combination AP1 AP2 AP3 AP4 AP2AP3 AP4 AP3 AP4 AP3 + AP4 SINR value (dB) 6 12 18 24 9 12 15 15 18 21 APcombination AP1 + AP2 + AP3 AP1 + AP2 + AP4 AP1 + AP3 + AP4 AP2 + AP3 +AP4 SINR value (dB) 12 14 16 18

It should be noted that although the above description described someexamples of the calculation as well as two equations which may be usedfor the calculation, they are not intended to be exclusive or belimiting to the present application. The calculation may be performedbased on any other available equations as long as those equations mayhelp to realize the principle of this application. For example, the STAmay perform the calculation based on variance equation, standardvariance equation, etc. It should also be noted that the above examplesas well as those parameter values are given by way of example, and theyare not intended to be limiting to the present application.

The following embodiments will describe how to generate the feedbackbased on the calculation result.

In an embodiment, the feedback may comprise at least one of the multipleAP combinations based on the calculation result obtained from theprocess at 1904. In other words, the STA may not transmit all of thecalculation result including all AP combinations obtain from thecalculation, but only a part of the AP combinations.

For example, when decoding the common information parts, the processormay obtain a fourth parameter (K) indicating that the STA may feedbackthe best K AP combinations to the AP group. In the above first examplewith Table 1, if K=6, then the feedback may comprise the following APcombinations: AP4 (SINR value=24); AP3+AP4 (SINR value=21); AP2+AP4(SINR value=18); AP3 (SINR value=18); AP2+AP3 (SINR value=15); andAP1+AP4 (SINR value=15). In this example, the AP(s) received thefeedback may select a specific AP combination from the above-mentioned 6AP combinations for multi-AP transmission. It should be noted that theabove example of K is only given by way of example, and it is notintended to be limiting to the present application. In an embodiment,the fourth parameter may be obtained by decoding the common informationpart(s). The method for obtaining the fourth parameter may be similar tothat for obtaining the first parameter described above. For example, ifthe transceiver received a first common information part from AP1, asecond common information part from AP2, and a third common informationpart from AP3, then the processor may decode a combination of the firstcommon information part and the second common information part to obtainthe fourth parameter. The processor may also decode a combination of allabove-mentioned three common information parts to obtain the fourthparameter.

In an embodiment, the feedback may comprise the calculation resultobtained from the process at 1904. That is, at the process 1905, the STAmay transmit all of the calculation result obtained to the APs in thegroup. As discussed above, the calculation result may comprise one ormultiple AP combinations as well as a new decoding metric (i.e., a thirdparameter) for each AP combination. In this embodiment, the APs in thegroup received the feedback may select a specific AP combination fromall of the multiple AP combinations obtained from the calculation (e.g.,AP combinations shown in Table 1) for multi-AP transmission.

Preferably, the feedback may comprise both at least one of the multipleAP combinations obtained from the calculation and a third parameterassociated with each of the at least one of the multiple APcombinations. In the above first example with Table 1, the feedback maybe shown as the following Table 4 (assuming K=6):

TABLE 4 AP1 + AP2 + AP2 + AP3 + AP combination AP3 AP4 AP4 AP3 AP4 AP4SINR value (dB) 18 24 15 15 18 21

The purpose of transmitting the obtained SINR values (i.e., thirdparameters) to the AP(s) in the group is to let the AP group know thethird parameter for each obtain AP combination. Then, the AP group mayselect a desired AP combination based on the third parameter formulti-AP transmission.

In an embodiment, the feedback may comprise an AP bitmap based on thecalculation result. The bitmap may be considered as a punctured APbitmap. In the punctured AP bitmap, the AP(s) not selected in an APcombination will not be shown or such AP(s) will be indicated to beunavailable. In that case, such AP(s) may be considered to be puncturedfrom the bitmap. The bitmap size may be the same as the number of APs inthe group, or number of beacons in the repetition beacon transmission.In the above third example with Table 3, if the STA wants to transmit afeedback including the AP combination AP2+AP3+AP4, the AP bitmap may beshown in the following Table 5:

TABLE 5 0 1 1 1

As shown in Table 5, each number represents an AP, and there are fourAPs (AP1-AP4 from the left end to the right end); “0” represents thatAP1 is not in this AP combination. “1” represents that AP2-AP4 are inthis AP combination. It should be appreciated that the bitmap includedin the feedback may vary based on the AP(s) in the AP combinations, andthe above example of bitmap shown in Table 5 is only given by way ofexample, and it's not intended to be limiting to the presentapplication.

In an embodiment, the feedback may comprise multiple fields and each ofthe multiple fields may comprise a third parameter and an AP identifieridentifying an AP combination. In other words, the STA may transmit afeedback comprising multiple fields each of which may combine an AP (orset of APs) identifier and the corresponding third parameter (e.g.,calculated SINR value). In the above first example with Table 1, a 4bit-field AP identifier may be defined such that each bit may correspondto a specific AP in the group. For example, “1010” may indicate AP1 andAP3 are selected in this AP combination. The feedback transmitted by theSTA in the above first example with Table 1 may be shown as thefollowing Table 6 (assuming K=6).

TABLE 6 Identifier 0010 0001 1001 0110 0101 0011 SINR value (dB) 18 2415 15 18 21

As shown in Table 6, a field consists of a pair of AP identifier andSINR value. There are 6 fields in total each of which represents an APcombination obtained from the calculation. It should be noted that theabove Table 6 as well as its 4 bit-field AP identifier indicating AP(s)in each AP combination is only given by way of example, and it's notintended to be limiting to the present application. Any other availableidentifier may be used to indicate AP combination(s) as long as they mayhelp to realize the above-mentioned principle of this application.

Preferably, the feedback may be ordered in multiple ways. That is, theAP combination(s) in the calculation result may be ordered in multipleways. For example, the AP combinations may be in a descending orderbased on SINR value. In the above first example shown with Table 1, thefeedback transmitted by the STA may be shown as the following Table 7(assuming K=6).

TABLE 7 AP2 + AP1 + AP2 + AP3 + AP combination AP4 AP3 AP4 AP4 AP3 AP4SINR value (dB) 24 18 18 15 15 21

As shown in Table 7, these 6 AP combinations are listed in a descendingorder based on their SINR values. The order of the AP combinations mayimplicitly identify the APs selected by the AP group. That is, the APgroup may select AP(s) based on the order of the AP combinationstransmitted in the feedback.

It should be noted that the above Table 7 as well as the exemplarydescending order is only given by way of example, and it's not intendedto be exclusive or be limiting to the present application. The APcombinations in the feedback may be listed in an ascending order basedon SINR values. In another embodiment, the AP combination in thefeedback may be listed based on the number of AP in each AP combination.For example, those AP combinations comprising two APs may be listedbefore those AP combinations comprising only one AP. It should be notedthat the order of AP combinations may be not limited to the bit-maporder as discussed above.

In an embodiment, the calculation result may indicate an AP combinationis not valid if the AP combination is unqualified. For example, in theabove second example shown with Table 2, those AP combinations whoseSINR value is lower than “0” may be considered to be unqualified, andthus, the AP combinations whose SINR value is lower than “0” may beindicated as “not valid”. In that case, in the above second example, theSTA may obtain the following AP combinations with SINR values shown inTable 8.

TABLE 8 AP AP1 + AP1 + AP1 + AP2 + AP2 + AP3 + combination AP1 AP2 AP3AP4 AP2 AP3 AP4 AP3 AP4 AP4 SINR value not not 3 9 not not 0 0 3 6difference valid valid valid valid (dB)

The process at 1905 will be discussed as follows. As shown in FIG. 19,at 1905, the method may comprise transmitting the feedback to at leastone of the plurality of APs. The AP(s) received the feedback may selectan AP or a plurality of APs from the group for multi-AP transmission.

In some embodiments, the STA may be able to connect to a single AP. Insome such embodiments, the STA may be polled by the primary AP (i.e.,the AP that the STA is associated with). The STA may be triggered by theprimary AP for UL OFDMA/UL MU-MIMO or UORA. The primary AP may send aNDP feedback trigger to the STAs and any STA that has feedback to sendmay indicate that it has a feedback to send. The primary AP may thentrigger or poll the STA. STA1 and STA2 shown in FIG. 24 may transmitfeedback based on the above-mentioned scheme. As shown in FIG. 24, AP1may transmit feedback (FB) poll 2401 to STAs (STA1-STA4), then it turnsout that only STA1 has a feedback (FB) 2404 to transmit. So, STA1 maytransmit FB 2404. Similarly, STA2 and STA3 may transmit FB poll 2402 andFB poll 2403 respectively, and it turns out that only STA2 has a FB 2405to transmit. It should be noted that the above-mentioned embodimentshown in FIG. 24 regarding the FB pool and FB transmissions is onlygiven by way of example, and it's not intended to be exclusive or belimiting to the present application.

In some embodiments, the STA is unable to connect to a single STA. A setof APs may send a feedback poll or NDP feedback trigger to STA(s). AnySTA that is unable to hear a single AP but is able to hear this poll ortrigger may transmit a feedback to the APs. STA3 and STA4 shown in FIG.24 may transmit feedback based on the above-mentioned scheme. As shownin FIGS. 24, AP1 and AP2 may be considered as a set of APs transmittinga feedback pool or NDP feedback trigger. Both of them may transmit thesame FB pool (2406, 2406′) to STAs, and it turns out that no STA has afeedback to transmit. AP1 and AP3 may be considered as a set of APstransmitting a feedback pool or NDP feedback trigger. Both of them maytransmit the same FB pool (2407, 2407′) to STAs, and it turns out thatSTA3 has a FB 2408 to transmit. AP2 and AP3 may be considered as a setof APs transmitting a feedback pool or NDP feedback trigger. Both ofthem may transmit the same FB pool (2409, 2409′) to STAs, and it turnsout that STA4 has a FB 2410 to transmit.

The APs may set their multi-AP transmission based on the feedback. Insome embodiments, a multi-AP announcement frame may include the AP(s)and STA(s) selected for the specific multi-AP transmission. In someembodiments, the above-mentioned feedback and calculation result (e.g.,fields, AP identifiers, bitmaps discussed above) may be exchangedbetween AP(s) and STA(s) using control frame, management frame, PLOPheader of any frame or MAC header of any frame. After selecting AP(s)based on the feedback transmitted from the STA at process 1905, theselected AP(s) may perform multi-AP transmission (e.g., multi-AP datatransmission) to the STA.

In another embodiment, at 1904, the STA may transmit the firstparameter, the plurality of second parameters and the number of theplurality of APs to at least one AP in the group. Then, theabove-mentioned calculation may be perform at AP side. That is, thefeedback generated by the processor at 1904 may include the firstparameter, the plurality of second parameters and the number of theplurality of APs. For example, the STA may obtain the first parameterindicating at most two APs in a desired AP combination; the total numberof APs, i.e., 4; the second parameter is SINR value of each AP; the SINRvalue of AP1 is 6, the SINR value of AP2 is 12; the SINR value of AP3 is18; and the SINR value of AP4 is 24. Then, the AP(s) received thefeedback may perform the above-mentioned calculation and obtain, basedon the calculation, a desired AP combination comprising one or more APs.In one method, the STA may feedback the quantized SINR values directlyto the APs. In one method, the STA may calculate the average SINR valueas SINR_average. Then calculate the difference between SINR_average andSINR values as SINR_diff_k=SINR_average-SINR_k. Here k is the AP index.The STA may feedback quantized SINR_diff_k values.

Then, the method 1900 may comprise: at 1906 receiving multi-APtransmission from a combination of one or more APs. Accordingly, thetransceiver may be further configured to receive multi-AP transmissionfrom a combination of one or more APs. Since the first parameter Mindicated the max number of selected APs (i.e., there are at most M APsin a desired AP combination), the multi-AP transmission may be performedby multiple APs in the group, i.e., the number of APs selected for themulti-AP transmission (i.e., the number of APs in a selected combinationof APs) should be less than or equal to M. Preferably, the multi-APtransmission may be performed by a combination of two or more APs.

Although features and elements are described above in particularcombinations, one of ordinary skill in the art will appreciate that eachfeature or element can be used alone or in any combination with theother features and elements. In addition, the methods described hereinmay be implemented in a computer program, software, or firmwareincorporated in a computer-readable medium for execution by a computeror processor. Examples of computer-readable media include electronicsignals (transmitted over wired or wireless connections) andcomputer-readable storage media. Examples of computer-readable storagemedia include, but are not limited to, a read only memory (ROM), arandom access memory (RAM), a register, cache memory, semiconductormemory devices, magnetic media such as internal hard disks and removabledisks, magneto-optical media, and optical media such as CD-ROM disks,and digital versatile disks (DVDs). A processor in association withsoftware may be used to implement a radio frequency transceiver for usein a WTRU, UE, terminal, base station, RNC, or any host computer.

1. A method for multiple access point (AP) transmission, the methodcomprising: receiving a plurality of repetition beacons, one from eachof a plurality of APs, each of the plurality of repetition beaconscomprising a common information part and an AP-specific informationpart; decoding at least one of the plurality of common information partsto obtain a first parameter; decoding the plurality of AP-specificinformation parts to obtain a plurality of second parameters, eachassociated with one of the plurality of APs; generating feedback basedon the first parameter and the plurality of second parameters and anumber of the plurality of APs; and transmitting the feedback to atleast one of the plurality of APs.
 2. The method of claim 1, wherein thegenerating feedback based on the first parameter and the plurality ofsecond parameters and a number of the plurality of APs comprises:performing a calculation based on the first parameter, the plurality ofsecond parameters and the number of the plurality of APs to obtain acalculation result; and generating the feedback based on the calculationresult.
 3. The method of claim 1 further comprising: receiving amulti-AP data transmission from a plurality of APs based on thefeedback.
 4. The method of claim 1, wherein the decoding at least onecommon information part to obtain a first parameter comprises: bufferingthe plurality of common information parts; combining the plurality ofcommon information parts; and decoding the plurality of commoninformation parts.
 5. The method of claim 1, wherein the number of theplurality of APs is obtained by decoding the plurality of AP-specificinformation parts.
 6. The method of claim 1, wherein in each repetitionbeacon the common information part and the AP-specific information partare aggregated together with no interframe spacing between them.
 7. Themethod of claim 1, wherein in each repetition beacon the commoninformation part and the AP-specific information part are transmittedwith an interframe spacing between them.
 8. The method of claim 1,wherein the second parameter is Signal to Noise Ratio (SNR) or Signal toInterference and Noise Ratio (SINR).
 9. The method of claim 2, whereinthe calculation result comprises a plurality of AP combinations.
 10. Themethod of claim 1, wherein the feedback comprises a plurality of fields,each of the plurality fields comprising a third parameter and anidentifier identifying a combination of two or more APs.
 11. A wirelesstransmit/receive unit (WTRU) for multiple access point (AP)transmission, comprising: a transceiver, configured to receive aplurality of repetition beacons, one from each of a plurality of APs,each of the plurality of repetition beacons comprising a commoninformation part and an AP-specific information part; and a processor,configured to decode at least one of the plurality of common informationparts to obtain a first parameter; decode the plurality of AP-specificinformation parts to obtain a plurality of second parameters, eachassociated with one of the plurality of APs; and generate feedback basedon the first parameter, the plurality of second parameters and a numberof the plurality of APs, wherein the transceiver is further configuredto transmit the feedback to at least one of the plurality of APs. 12.The WTRU of claim 11, wherein to obtain the feedback, the processor isfurther configured to: perform a calculation based on the firstparameter, the plurality of second parameters and the number of theplurality of APs to obtain a calculation result; and generate thefeedback based on the calculation result.
 13. The WTRU of claim 11, thetransceiver is further configured to receive a multi-AP datatransmission from a plurality of APs based on the feedback.
 14. The WTRUof claim 11, wherein to decode at least one common information part toobtain a first parameter, the processor is further configured to bufferthe plurality of common information parts; combine the plurality ofcommon information parts; and decode the plurality of common informationparts.
 15. The WTRU of claim 11, wherein the number of the plurality ofAPs is obtained by decoding the received AP-specific information parts.16. The WTRU of claim 11, wherein in each repetition beacon the commoninformation part and the AP-specific information part are aggregatedtogether with no interframe spacing between them.
 17. The WTRU of claim11, wherein in each repetition beacon the common information part andthe AP-specific information part are transmitted with an interframespacing between them.
 18. The WTRU of claim 11, wherein the secondparameter is Signal to Noise Ratio (SNR) or Signal to Interference andNoise Ratio (SINR).
 19. The WTRU of claim 12, wherein the calculationresult comprises a plurality of AP combinations.
 20. The WTRU of claim11, wherein the feedback comprises a plurality of fields, each of theplurality fields comprising a third parameter and an identifieridentifying a combination of two or more APs.